bluuebunny/crossref_metadata_2025 huggingface dataset:
GROWTH OF THE BARLEY COLEOPTILE. I. ITS RELATIONSHIP TO CELL NUMBER AND LENGTH IN NORMAL AND γ‐IRRADIATED SEEDLINGS
Authors: Liptay A. , Davidson D.
Published: January 2018

The number of cells per vertical column in barley coleoptiles differs in various growth classes; it is highest in tall coleoptiles, intermediate in medium ones, and lowest in short ones. In those that elongate early and grow rapidly, cells per column increased from 88–218 between 12 and 44 hr after the seeds were placed on water; in short coleoptiles they increased to only 85 per column after 115 hr because elongation and division are restricted in these. Cell number does not increase in coleoptiles from seeds irradiated with 250 krad. Variation in the growth pattern of irradiated coleoptiles was similar to that of normal ones, although the range in lengths was reduced. Although the number of cells is much higher in tall controls than in irradiated coleoptiles, the latter can become tall; therefore an increase in cell number during germination does not seem to be a prerequisite for tallness. Coleoptiles 32 mm long, from irradiated seeds, have the same number of cells per column as the shortest ones (6 mm) after 119 hr.
ADAPTIVE LEAF ARCHITECTURE IN EMERGENT AND FLOATING SPARGANIUM
Authors: Kaul Robert B.
Published: January 2018

The robust emergent leaves of Sparganium eurycarpum and S. americanum are supported by corner fiber masses and large bundle sheaths, but the thin floating leaves of S. fluctuans and S. minimum have only moderate bundle sheaths. In emergent types heavily photosynthetic diaphragms bearing vascular bundles are separated from each other in the leaf compartments by three lightly photosynthetic diaphragms without bundles, but in floating types only every other heavily photosynthetic diaphragm has a bundle. Palisade chlorenchyma occurs only at aerial surfaces—abaxial and adaxial in emergent leaves, but only adaxial in floating leaves. Extra photosynthetic areas are provided in emergent leaves by concentrations of chlorenchyma in limited areas on interior partitioning walls, while the remainder of the walls is translucent. Since only 25 % of the diaphragms are heavily photosynthetic, and the others essentially transparent because of their diffusely distributed chloroplasts and large intercellular spaces, a sieve effect exists which allows even the interior parts of thick emergent leaves to photosynthesize.
EFFECTS OF DAY AND NIGHT TEMPERATURE AND TYPE OF CONTAINER ON THE GROWTH OF F1 HYBRID ANNUALS IN CONTROLLED ENVIRONMENTS
Authors: Krizek Donald T. , Klueter Herschel H. , Bailey William A.
Published: January 2018

The effects of three day/night temperatures (18/12 C, 24/18 C, and 30/24 C), and two types of containers (clay and plastic) on the seedling growth of three F1 hybrid annuals were determined after 14 days of controlled‐environment treatment. A day/night temperature of 18/12 C was severely limiting to the early seedling growth of ‘Blue Blazer’ ageratum (Ageratum houstonianum Mill.), ‘Pink Cascade’ petunia (Petunia hybrida Vilm.), and ‘Double Eagle’ marigold (Tagetes erecta L.). Raising the day/night temperature to 24/18 C resulted in striking increases in growth in both clay and plastic pots. Fresh and dry weights of tops for all three species were increased four‐ to fivefold, and leaf areas of ageratum and petunia were increased more than fivefold irrespective of container. Height and node number were also increased significantly but to a much lesser degree. A day/night temperature of 30/24 C appeared to be optimum for early seedling growth of F1 hybrid annuals the optimum being based on dry matter accumulation, stem elongation, node development, and leaf area production. Growth of lateral shoots was greatly stimulated at 30/24 C, especially in marigold. There were no appreciable differences in fresh or dry weight of tops or in leaf area between plants in clay and plastic containers at any of the three day/night temperatures.
ELECTRON MICROSCOPY OF PHIALOCONIDIOGENESIS IN METARRHIZIUM ANISOPLIAE
Authors: Hammill Terrence M.
Published: January 2018

Fine‐structure observations with two different fixation procedures showed that phialide necks possessed a thickened electron‐transparent wall layer. Phialoconidia developed from a wall layer which originated 1–1.5 μm within phialide necks. After conidium initials blew out of phialide tips and organelles entered, conidia were delimited by transverse septa which did not appear to be plugged by Woronin body‐like plugs. Instead, septa appeared to become functionally complete by continued centripetal growth. Conidium‐delimiting septa moved distally out of phialide necks as subsequent conidium initials formed. During this distal movement, septa increased in thickness and lamellae appeared on the conidium side; mature conidia had bipolarly lamellate cell walls. Conidial walls had a thin, ridged electron‐dense outer wall layer and a thicker electron‐transparent inner wall layer which increased in thickness centripetally after septum delimitation. Conidia were usually uninucleate and possessed conspicuous storage vacuoles with lipid and protein contents. Conidia also possessed numerous presumably lipid droplets. Multivesicular bodies were observed near conidium‐delimiting septa and conidium walls which were increasing in thickness.
PHENODYNAMIC ANALYSES OF TWO FIRST‐YEAR OLD FIELDS
Authors: Swieringa Susan , Wilson Roger E.
Published: January 2018

Phenological spectra from two adjacent first‐year old fields suggest that phenological events may be directed by the biotic influences of associated species as well as by climatic and edaphic conditions of the region. These two fields possessed similar macroclimatic conditions but had differing soil textures and crop histories. Phenological spectra were developed by observations made on all plant species occurring in fixed quadrats during the duration of this study, April 1, 1970, to October 20, 1970. The phenophases observed were initiation of vegetative growth, time of budding, occurrence of flowering, fruiting sequences, and time of seed set and dissemination. Production studies based on short‐term harvest methods indicated the dominance of Erigeron canadensis in the abandoned soybean field, and Erigeron annus in the abandoned corn field.
MORPHOGENETIC STUDIES ON HAWORTHIA: ESTABLISHMENT OF TISSUE CULTURE AND CONTROL OF DIFFERENTIATION
Authors: Kaul K. , Sabharwal P. S.
Published: January 2018

Investigations were carried out on the in vitro morphogenetic responses of inflorescence segments and gynoecia of several species of Haworthia (Liliaceae). Morphogenetic responses of explants were not species specific. It was found that coconut milk was essential for the growth and differentiation of Haworthia tissue if White's basal medium was used. However, growth and differentiation could be supported by a modified Murashige and Skoog's medium, without any supplements. The investigations demonstrated’ the importance of inositol and ammonium nitrogen in the nutrition of Haworthia tissue cultures. A chemical control of callusing and shoot and root differentiation was obtained by providing appropriate amounts of auxin and cytokinin in the culture medium.
PHYSIOLOGICAL IMPLICATIONS OF VICIA FABA AND NICOTIANA TABACUM GUARD‐CELL ULTRASTRUCTURE
Authors: Pallas James E. , Mollenhauer Hilton H.
Published: January 2018

The guard cells of Vicia faba and Nicotiana tabacum contain numerous mitochondria, elements of endoplasmic reticulum, spherosomes, and peroxisome‐like microbodies. A full ribosomal complement appears in young but not in fully mature guard cells. Numerous small lipid droplets external to the plasmalemma were noted in mature Vicia guard cells. Chloroplasts were found in both epidermal and guard cells of both species. Full photosynthetic capacity was indicated by the grana fretwork of guard‐cell chloroplasts. A specialized peripheral reticulum was observed in the guard‐cell chloroplasts of Vicia. Plasmodesmata were observed in both walls between sister guard cells and between guard and epidermal cells. In the latter case plasmodesmata were found primarily in pit fields of transverse walls. It is postulated that the small volume of guard cells allows them an osmotic advantage over larger neighboring cells in generating turgor.
COMPARATIVE MORPHOLOGY OF THE PRIMARY VASCULAR SYSTEMS IN SOME SPECIES OF ROSACEAE AND LEGUMINOSAE
Authors: Devadas Crispin , Beck Charles B.
Published: January 2018

The structural patterns of the primary vascular systems in some species of Leguminosae and Rosaceae have been determined by tracing the longitudinal course of the vascular bundles in terminal stem segments. These systems are interpreted as consisting of sympodia. Each sympodium is composed of an axial bundle which is continuous through the length of the segment and from which arise trace bundles that supply leaves and axillary buds. A compact arrangement of vascular bundles seems to correlate with the woody habit. Regardless of the degree of compactness of the primary vascular system, the structural identity of the individual sympodia is maintained. The total number of vascular bundles at a particular level is related to the number of axial bundles in the system, the number of traces per leaf and per axillary bud, and the number of internodes traversed by the traces prior to entering a lateral appendage. Shrubs and trees have more vascular bundles than herbs. Data from this study and the literature indicate that the vascular system is predominantly of the open type in dicotyledonous plants which have helically arranged leaves and, further, that in such plants with a 3‐trace, trilacunar nodal structure, the number of sympodia coincides with the number of orthostichies (which is also the denominator of the phyllotactic fraction). In open systems leaf gaps cannot be morphologically delimited. Because of the resemblance of the open type of angiosperm vascular system to that of certain gymnosperms, previously interpreted to have evolved from a protostele, we suggest that the eustele of angiosperms is homologous with the stele of gymnosperms. We believe, also, that angiosperms, like gymnosperms, are probably not characterized by leaf gaps of filicinean type. We provide, furthermore, a rationale for the view that the axial bundle of a sympodium is a cauline structure.
ALLELOPATHIC EFFECTS OF ANDROPOGON VIRGINICUS AND ITS PERSISTENCE IN OLD FIELDS
Authors: Rice Elroy L.
Published: January 2018

Aqueous extracts of fresh roots and shoots of Andropogon virginicus (broomsedge) were found to be inhibitory to the growth of seedlings of Amaranthus palmeri, Bromus japonicus, Aristida oligantha, and Andropogon scoparius. The first two species are often important in the pioneer stage of old‐field succession in eastern Oklahoma, Aristida is prominent in the second stage, and Andropogon scoparius is important later in succession including the climax Quercus stellata–Quercus marilandica savanna. Sterile dilute extracts of roots and shoots of broomsedge were inhibitory to two test species of Azotobacter, a free living nitrogen fixer, and to two species of Rhizobium, a symbiotic nitrogen fixer. Small amounts of decaying shoots of broomsedge (1 g per 454 g of soil) were very inhibitory to the growth of the four test species listed above and to Amaranthus retroflexus, another species often important in the first stage of succession. Similar amounts of decaying material in soil also significantly inhibited growth and nodulation of the two most important species of legumes in old‐field succession in eastern Oklahoma, Lespedeza stipulacea and Trifolium repens. Broomsedge is known to compete vigorously and grow well on soils of low fertility, so the inhibition of nodulation of legumes could help keep the nitrogen supply low and give broomsedge a selective advantage in competition over species that have higher nitrogen requirements. The combined interference of broomsedge against other species resulting from competition and allelopathy could help explain why it invades old fields in 3–5 yr after abandonment from cultivation and remains so long in almost pure stands.
THE ULTRASTRUCTURAL MORPHOLOGY AND ONTOGENY OF OAT COLEOPTILE PLASTIDS
Authors: Hinchman Ray R.
Published: January 2018

Structurally similar proplastids occur in the shoot, scutellum, and root of the oat embryo at the start of germination. These proplastids follow several pathways of differentiation, depending on their location within an organ and on previous exposure to light. During the first 24 hr of germination morphologically similar amyloplasts are formed from the preexisting proplastids in most of the cells of the seedling. After about 24 hr in the light, unique chloroplasts begin to develop in a subepidermal ring of small cortical parenchyma cells in the coleoptile and give the organ a pale green color. At 48 and 72 hr the coleoptile chloroplasts and etioplasts are conspicuously different from the corresponding leaf plastids in morphology and ontogeny but contain typical photosynthetic grana and prolamellar bodies. Study of the ontogeny of plastids in the epidermal and nongreening parenchymal regions of dark grown coleoptiles shows that these plastids undergo significant losses in starch content, and some increase of membranes within the plastid, related to the age of the cell. Light has little effect on the structure of these plastids. It is suggested that the ontogeny of all the plastid types of the oat seedling begins with a common precursor—a relatively simple proplastid that is present at the time of germination. Starch grains showing two distinct types of erosion, apparently enzymatic, were observed in oat coleoptile plastids. In one type (grooved appearance) the starch grains are consistently associated with plastid membranes, while in the other type (irregular, spiny appearance) the starch grains are associated with the plastid stroma only. We suggest that there are two enzyme systems for metabolizing starch in oat plastids—one membrane‐bound and the other free in the stroma.
QUANTITATIVE MICROSPECTROPHOTOMETRY OF NUCLEAR DNA IN SELFING STRAINS OF THE MYXOMYCETE DIDYMIUM IRIDIS
Authors: Yemma John J. , Therrien C. Dale
Published: January 2018

Genetic and cytochemical investigations of the origin, development, nuclear activity, and ploidy level of Plasmodia obtained from selfed clones S‐2 and B1P‐33 of the heterothallic myxomycete, Didymium iridis, are presented. To demonstrate that selfing did not result from contamination of the clones, or mutations at the mating‐type locus, crosses were made between F1 clones and clones of known mating types. The data were inconsistent with these two possibilities. DNA was quantified by Feulgen‐DNA microspectrophotometry. All cellular phases studied (logarithmic amoebae, swarmers, and encysted amoebae) appear to be haploid, with the nuclear DNA being in the replicated (2C) state. The plasmodia are in all cases diploid; however, the data indicate that the selfed Plasmodia are in an extended G1 condition. The nuclear DNA content of these is therefore 2C, whereas that of the cross Plasmodium is 4C. Sporangial nuclei exhibit DNA in diploid replicated (4C) category.
CERTAIN EMBRYOLOGICAL AND BIOCHEMICAL ASPECTS OF CYTOKININ SD 8339 IN CONVERTING SEX OF A MALE VITIS VINIFERA (SYLVESTRIS)
Authors: Negi S. S. , Olmo H. P.
Published: January 2018

Certain embryological and biochemical effects of the cytokinin (SD 8339) in converting flower sex from male to hermaphrodite were studied in a clone of Vitis vinifera L. (sylvestris). The cytokinin accelerated the meiotic division of the megaspore mother cell, mitotic divisions of the megaspore and cells of pistillate tissue, and increased the rate of protein synthesis in flower buds. Two working hypotheses for the possible mode of action of the cytokinin in sex conversion are presented.
PERTICA, A NEW GENUS OF DEVONIAN PLANTS FROM NORTHERN MAINE
Authors: Kasper Andrew E. , Andrews Henry N.
Published: January 2018

A new genus of Devonian age fossil plants is described from the Trout Valley Formation of northern Maine. Abundant compression material permits a rather complete understanding of its morphology. Pertica quadrifaria Kasper and Andrews, gen. et sp. nov., was an erect plant, perhaps a meter tall, with a pseudomonopodial main axis and dichotomous side branches. The side branches were arranged in a clockwise spiral (from base to apex) and were tetrastichous. They dichotomized numerous times, with the intervals between dichotomies decreasing distally. The ultimate branchlets bore numerous sporangia in dense clusters. Other side branches were completely sterile. Pertica quadrifaria is classified in the Subdivision Trimerophytina of Banks. Its evolutionary significance rests in the fact that it is a link in the chain of increasingly complex early vascular land plants.
CONIDIOGENESIS IN CERATOCYSTIS ULMI, CERATOCYSTIS PICEAE, AND GRAPHIUM PENICILLIOIDES
Authors: Crane J. L. , Schoknecht Jean D.
Published: January 2018

Conidiogenous cells of both the synnematous and mononematous conidiophores inCeratocystis ulmiandC. piceaedevelop by sympodial proliferation. Holoblastic conidia are produced on nodules or short denticles from the synnematous conidiogenous cells and on well‐defined denticles from the mononematous conidiogenous cells.Graphium penicillioidesis characterized by percurrent proliferation of the conidiogenous cells and the conidia are holoblastic and annellidic. A comparison of the type material ofG. penicillioideswith the lectotype specimen ofC. piceaeindicates thatG. penicillioidesis not the conidial state ofC. piceae. The method of conidial development inC. ulmiandC. piceaeis distinct from that ofG. penicillioides, the lectotype species ofGraphium;these conidial states are, therefore, placed in a new hyphomycete genus,Pesotum, as thePesotumstate ofCeratocystis ulmiandC. piceae, respectively.
ULTRASTRUCTURAL STUDIES OF ABSCISSION IN PHASEOLUS: ETHYLENE EFFECTS ON CELL WALLS
Authors: Webster Barbara D.
Published: January 2018

This paper reports light and electron microscope observations of changes in the walls of cortical cells in the laminar abscission region of red kidney bean (Phaseolus vulgaris L.). In intact plants two or three rows of cells comprise the abscission zone. Pectic substances are not present in the walls of these cells when wall breaks occur. The separation cavity involves breaks in both radial and longitudinal cell walls. In ethylene‐treated explants pectic substances are present in the cell walls when breaking occurs. The separation cavity involves breaks in longitudinal walls only, and breaking is confined to a single row of cortical cells. Prior to cell wall break the plasma membrane frequently invaginates. In intact plants this may be associated with plasmolysis and with the formation of secondary vacuoles. In ethylene‐treated explants it may also be related to plasmolysis. At the time of cell wall break many unidentifiable inclusions of varying sizes and shapes are present in the cell wall region. Chloroplasts and mitochondria are structurally altered but recognizable in the cell at the time of wall break. Plasmodesmata are frequently observed in abscission cells and may be structurally elaborate. The observations of the nature of cell wall changes during abscission in ethylene‐treated material fail to confirm physiological studies of other workers suggesting that pectin dissolution is necessary and may be sufficient for formation of a separation layer.
CORRELATION ANALYSIS OF RAINFALL AND ANNUAL RING INDEX OF CENTRAL OKLAHOMA BLACKJACK AND POST OAK
Authors: Johnson Forrest L. , Risser Paul G.
Published: January 2018

Yearly ring‐width indices were determined for Quercus stellata and Q. marilandica in central Oklahoma for the period 1892–1971 and were used as dependent variables in correlation analyses with corresponding series of previous growth rates and various precipitation totals as independent variables. Results of multiple correlation show that approximately 60% of the variance in ring indices of both species can be accounted for by precipitation and previous growth rates. Simple linear correlation analysis of precipitation data shows that the ring index value for a year is significantly correlated with rainfall in the current spring and in the previous summer.
AN AUTORADIOGRAPHIC ANALYSIS OF THE ROOT EPIDERMIS OF THE SWITCH GRASS (PANICUM VIRGATUM)
Authors: Abreu Sergio L. , Rothwell Norman V. , Lewis Robert F.
Published: January 2018

Analyses of 3H‐uridine, 3H‐thymidine, and 3H‐lysine incorporation in the root epidermis of Panicum virgatum were undertaken. Highly significant differences between the mean incorporation of 3H‐uridine and 3H‐lysine in epidermal and adjacent cortical cells were observed. While the cortex exhibited a steady decrease of precursor incorporation with distance from the apex, the epidermal cells exhibited differential incorporation. These results were regarded as further evidence for the hypothesis that cells of two maturation potentials exist in the epidermis of this panicoid grass. Treatment with 20.0 μg/ml of actinomycin D resulted in a differential inhibition in the epidermal‐cortical incorporation of 3H‐uridine. The possibility of endopolyploidy in the epidermis was suggested by the observation that root hairs, hair initials, and some epidermal cells incorporated two to four times more 3H‐thymidine than meristematic cells. Neither puromycin nor actinomycin D treatment affected the protein‐positive particles present in the cytoplasm of epidermal cells in this grass. Similarly, RNase did not affect their structural integrity. Attempts to clarify the significance of these inclusions and their possible role, if any, in the differentiation of the epidermis are now in progress.
A NEW CONIFER FROM THE UPPER CRETACEOUS OF CENTRAL CALIFORNIA
Authors: Page Virginia M.
Published: January 2018

Stems with inner bark, wood, pith, and leaves from the Upper Cretaceous (Maastrichtian) of central California are described. The name Margeriella cretacea gen. et sp. n. is assigned to the fossils. The leaves are long, narrow, spirally arranged, and each contains three resin canals, a thick vascular sheath, and a dense mesophyll. Only first‐year wood is present in the stem. The large pith is composed of large cells among which are scattered clusters of even larger darkly colored cells. Leaf epidermis and wood characters suggest affinities with the Taxodiaceae, but the structure of the pith and the internal structure of the leaves have no counterpart among modern or known fossil members of that family. The fossil is regarded as an extinct form possibly belonging to the large taxodioid complex thought by some workers to have existed in the Mesozoic.
PROPOSED ORIGIN OF TETRAPLOID SPECIES OF CRESTED WHEATGRASS BASED ON CHROMATOGRAPHIC AND KARYOTYPIC ANALYSES
Authors: Taylor Ronald J. , McCoy Gene A.
Published: January 2018

Chromatographic techniques were used and the results were correlated with karyotypic studies in an attempt to determine the origin of five tetraploid “species” of crested wheatgrass, Agropyron desertorum, A. fragile, A. imbricatum, A. sibiricum, and A. pectimforme. Chromatograms of phenolic extracts of all tetraploid taxa and two diploids, A. imbricatum and A. pectiniforme—Fairway type, were developed using two‐dimensional paper chromatography, and comparative analyses were made. The analyses were of three types: one in which the pigments were quantified and assigned weighted values; the second a qualitative analysis in which only the presence or absence of the pigments was considered; the third, a similar qualitative analysis of hydrolysates. Similarity indices were computed for all combinations of taxa in each of the comparative chromatographic analyses, and phenograms were prepared. The two diploid taxa were chromatographically distinct, and all tetraploid forms were intermediate with the exception of A. pectiniforme, which exhibited the same phenolic profile as the diploid A. pectiniforme—Fairway type, and two of its colchicine‐induced tetraploids. From these data it is postulated that A. pectiniforme is a natural autopolyploid, and the other tetraploids included herein were derived through hybridization of A. imbricatum and A. pectiniforme— Fairway type, with subsequent allopolyploidy. This is in accord with karyotypic studies of McCoy and Law (unpublished).
DEVELOPMENTAL ANATOMY IN ROOTS OF IPOMOEA PURPUREA. II. INITIATION AND DEVELOPMENT OF SECONDARY ROOTS
Authors: Seago James L.
Published: January 2018

In seedlings of Ipomoea purpurea secondary roots are initiated in the primary root pericycle opposite immature protoxylem. Cells derived from immature endodermis, pericycle, and incipient protoxylem and stelar parenchyma contribute to the primordium. The derivatives of the endodermis become a uniseriate covering over the tip and flanks of the primordium and emerged secondary root; the endodermal covering is sloughed off when the lateral root reaches 1–5 mm in length. A series of periclinal and anticlinal divisions in the pericycle and its derivatives gives rise to the main body of the secondary root. The initials for the vascular cylinder, cortex, and rootcap‐epidermis complex are established very early during primordium enlargement. After emergence from the primary root, the cortical initials undergo significant structural modifications related to enlargement of the ground meristem and cortex, and the rootcapepidermal initials are partitioned into columellar initials and lateral rootcapepidermal initials. Procambium diameter increases by periclinal divisions in peripheral sectors. The mature vascular cylinder is comprised of several vascular patterns, ranging from diarch to pentarch, that are probably related ontogenetically. Cells derived from incipient protoxylem and stelar parenchyma cells of the primary root form the vascuar connection between primary and secondary roots.
THE CAIRO FLORA (GIVETIAN) FROM EASTERN NEW YORK. I. REIMANNIA, TERETE AXES, AND CAIROA LAMANEKII GEN. ET SP. N.
Authors: Matten Lawrence C.
Published: January 2018

A collection of over 200 petrified Middle Devonian plants was made from a single locality near Cairo, New York. This paper represents the second of a series enumerating the plants of the flora. Reimannia aldenense with a single lateral appendage containing a terete xylem strand that divides is present. Reimannia is thought to represent young branches within the Aneurophytales. Many of the sections made for the study of the flora contain small, terete axes. Some have a very distinctive epidermis. Some dichotomize several times. Cairoa lamanekii gen. et sp. n. shows closest affinity to the Aneurophytales yet differs in that the shape of the primary xylem is not consistently repeated from one order of axis to the next. It is suggested that Cairoa and Proteokalon represent a distinctive subgroup in the Aneurophytales.
ORGANIZATION OF THE MORPHOPHYSIOLOGIC UNIT IN ANAGALLIS ARVENSIS AND ITS RELATION WITH THE PERPETUATION MECHANISM AND SENESCENCE
Authors: Trippi Victorio S. , Brulfert Jeanne
Published: January 2018

The organization of the morphophysiological unit in Anagallis arvensis L. is conditioned by vegetative growth, which is expressed as indeterminate under short‐day conditions and as determinate under long‐day ones. The perpetuation mechanism is a function of the environment. Under SD conditions ontogenetic morphogenesis is incomplete, and the unit does not form specific reproductive structures; indeterminate growth and permanent rooting capacity provide an efficient mechanism for perpetuation. Under LD complete ontogenetic morphogenesis assures perpetuation by seeds. The appearance of senescence is independent of the nature of the morphophysiological unit and is directly related to growth cessation. It affects organs only when growth is indeterminate (SD) and the whole organism when growth is determinate (LD). Organ senescence seems related to growth itself, and organism senescence would appear closely related to photoperiodic effects. Photoperiod controls organization of the unit, ontogenetic morphogenesis, and organism senescence simultaneously. The number of leaves per node, flowering, organization, and senescence of the organism are all directed toward a more or less evolved state by the effects of the photoperiodic condition.
THE CHROMOSOMES OF PACHYPHYTUM (CRASSULACEAE)
Authors: Uhl Charles H. , Moran Reid
Published: January 2018

Eleven of the 12 species of Pachyphytum, all that are available, have n = 31–33 standard chromosomes, or a multiple. Accessory chromosomes were found in some or all collections of four species; some cells of one plant have more than 50 of them. Accessory chromosomes often occur in groups at metaphase I, corresponding to their origin from one to several chromocenters of prophase I. Intraspecific polyploidy occurs within five species, with diploids to 12‐ploids (n = ca. 186) in P. compactum and diploids to decaploids (n = ca. 160) in P. hookeri. Although the basic chromosome number is high, evidence from meiosis in certain hybrids shows that the basic 31–33 chromosomes are probably all different: they do not pair with each other and they do not duplicate each other. Polyploids, with 62 or more chromosomes, are probably autopolyploids: they form multivalents, and the chromosomes they contribute to hybrids pair with each other. Three different probable hybrids have been found in the wild, and more than 300 hybrids have been produced in cultivation.
THE ROOT APEX OF MALVA SYLVESTRIS. III. LATERAL ROOT DEVELOPMENT AND THE QUIESCENT CENTER
Authors: Byrne John M.
Published: January 2018

Both histological and autoradiographic procedures were used to follow lateral root initiation and development. Lateral roots of M. sylvestris were initiated in the pericycle, and although the endodermis became multiseriate, endodermal derivatives were not incorporated into the lateral root primordium. Apical organization of pre‐emergent roots, characterized by two tiers of cortical initials, did not change with growth. During pre‐emergent development there was no evidence of cortical lysogeny or quiescent center formation. Quiescent centers were present in both secondary and tertiary roots longer than 0.5 cm.
THE MORPHOLOGY OF CUBICULOSPORUM KORONICARPIS GEN. ET SP. NOV., REPRESENTING A NEW FAMILY IN THE GIGARTINALES (RHODOPHYTA)
Authors: Kraft Gerald T.
Published: January 2018

The red alga Cubiculosporum koronicarpis gen. et sp. nov. is described from material collected during 1968 in the Philippines. The species differs substantially in regard to its carposporophyte development from other red algae in the order Gigartinales, and a new family is created based on its unique combination of reproductive features. A single, short, connecting filament is formed between the fertilized carpogonium and a nearby auxiliary cell. The latter produces several ramifying gonimoblast filaments towards the interior of the thallus. No fusion cell is formed and the gonimoblast filaments grow inward among the cells of the central axis, form secondary connections to them, and give rise to outwardly directed carposporangial filaments that develop within peripheral chambers formed between elongating inner cortical cells. The alga is a low, clump‐forming species of well‐washed intertidal reef platforms at the one Philippine locality where it has been found. There it contributed a uniform but very minor amount to the wet weight of the standing crops that were studied during two separate seasons of the year.
PHOTOPERIODIC AGING IN ANAGALLIS ARVENSIS CLONES: ITS RELATION TO RNA CONTENT, ROOTING CAPACITY, AND FLOWERING
Authors: Trippi Victorio S. , Brulfert Jeanne
Published: January 2018

We investigated the photoperiodic regulation of aging in Anagallis arvensis L. propagated by cuttings. Short‐day (SD) conditions caused the persistence of juvenile forms and vegetative growth, as well as high rooting capacity and a high RNA content, through successive vegetative multiplications. SD + 1 long day (LD) every 15th day induced reproductive growth but allowed the persistence of a high rooting capacity and high RNA content through vegetative multiplications. LD conditions caused the persistence of the reproductive stage, the progressive loss of rooting capacity, and a decrease of RNA content. The longevity of the clones seems to be connected to the photoperiodic effects which induce indeterminate growth (SD) and/or determinate and reproductive growth. The loss of propagation capacity and the decrease of RNA content can be considered as indexes of aging not only in plants but also in clones.
RING‐POSITION AND FREQUENCY OF CHIASMA FAILURE IN RHOEO SPATHACEA
Authors: Lin Yue Jee , Paddock Elton F.
Published: January 2018

The mean chiasma number per cell was 11.44 ± 0.04 in 489 cells. Due to chiasma failures, the ring‐of‐twelve chromosomes may be broken into two or three chains. Cells with four or more chains were not observed. All six possible two‐chain situations and eight different threechain situations were found. All possible lengths of chains from one to all twelve chromosomes were found, with “chain”‐of‐one inordinately frequent. The overall mean number of chromosomes in 273 chains in 188 cells is 8.26 ± 0.31 and 5.38 ± 0.31 among 154 chains in the 69 cells that had two or more chains. The mean number of chains per cell among these 188 was 1.45 ± 0.13. In 73 cells, 113 chiasma failures were found to be distributed at random among the twelve chromosome arm positions. The absence of association either between length of arm or between presence‐absence of secondary constriction and frequency of chiasma failure support the generally accepted theory that, in Rhoeo, synapsis and crossing over are restricted to small terminal segments on all chromosomes.
PHLOEM OF SPHENOPHYLLUM
Authors: Eggert D. A. , Gaunt D. D.
Published: January 2018

The phloem of most fossil plants, including that of Sphenophyllum, is very poorly known. Sphenophyllum was a relatively small type of fossil arthrophyte with jointed stems bearing whorls of leaves ranging in form from wedge or fan‐shaped to bifid, to linear. The aerial stem systems of the plant exhibited determinate growth involving progressive reduction in the dimensions of the stem primary bodies, fewer leaves per whorl, and smaller and simpler leaves distally. The primary phloem occurs in three areas alternating in position with the arms of the triarch centrally placed primary xylem. Cells of the primary phloem, presumably sieve elements, are axially elongate with horizontal to slightly tapered end walls. In larger stems with abundant secondary xylem and secondary cortex or periderm, a zone of secondary phloem occurs whose structure varies in the three areas opposite the arms of the primary xylem, as opposed to the three areas lying opposite the concave sides of the primary xylem. The axial system of the secondary phloem consists of vertical series of sieve elements with horizontal end walls. In the areas opposite the protoxylem the parenchyma is present as a prominent ray system showing dilation peripherally. Sieve elements in the areas opposite the protoxylem arms have relatively small diameters. In the areas between the protoxylem poles the secondary phloem sieve elements have large diameters and are less obviously in radial files, while the parenchyma resembles that of the secondary xylem in these areas in that it consists of strands of cells extending both radially and tangentially. An actively meristematic vascular cambium has not been found, indicating that this layer changed histologically after the cessation of growth in the determinate aerial stem systems and was replaced by a post‐meristematic parenchyma sheath made up of axially elongate parenchyma lacking cells indicative of being either fusiform or ray initials. A phellogen arose early in development in a tissue believed to represent pericycle and produced tissue comparable to phellem externally. Normally, derivatives of the phellogen underwent one division prior to the maturation of the cells. Concentric bands of cells with dark contents apparently represent secretory tissue in the periderm and cell arrangements indicate that a single persistent phellogen was present. Sphenophyllum is compared with other arthrophytes as to phloem structure and is at present the best documented example of a plant with a functionally bifacial vascular cambium in any exclusively non‐seed group of vascular plants.
STUDIES OF SPERMATOGENESIS IN THE HEPATICAE. IV. ON THE BLEPHAROPLAST OF BLASIA
Authors: Carothers Zane B.
Published: January 2018

Spermatogenesis in Blasia pusilla L. was reexamined with electron optics to help evaluate conflicting results of the two earlier light microscope studies of this species. The present micrographic resumé of spermatid transformation confirms Sharp's observation of centrosomes in very young spermatids and agrees with Woodburn's general account of spermatozoid maturation. Further, male gamete development in Blasia is shown to be closely comparable to that of Marchantia and Pellia. It is concluded that Sharp's report of blepharoplast development in Blasia by fragmentation and coalescence was based on anomalous plant material.
THE CYTOLOGY OF SOME SPECIES OF THE GENUS NOTHOLAENA
Authors: Knobloch Irving W. , Tai William , Ninan Thamby A.
Published: January 2018

Eight taxa in the genus Notholaena were examined for their chromosome numbers; one of the eight had two cytotypes (2 N, 4 N). The other seven consisted of five triploids and two diploids. Observations were also included on spore number and prothallial glandularity whenever possible.
STARCH GEL ELECTROPHORESIS OF ENZYMES FROM NINE SPECIES OF POLYPORUS
Authors: Shannon Michael C. , Ballal S. K. , Harris John W.
Published: January 2018

Taxonomic relationships among 22 isolates of nine species of the wood‐rotting fungus, Polyporus, were examined by starch gel electrophoresis, coupled with histochemical staining procedures. Crude extracts of 21‐day cultures grown on malt extract agar were subjected to electrophoresis for 3 hr at a constant current of 25 ma. Esterase, peroxidase, catechol oxidase, galactose dehydrogenase, acid phosphatase, and alkaline phosphatase banding patterns were analyzed. With each enzyme, the bands for each isolate were compared with those for other isolates of the same species and for isolates of other species. A closer relationship was found in the banding patterns for different isolates of a single species than among isolates of different species. This technique may prove valuable for the evaluation of taxonomic differences among these wood‐rotting fungi.
STOMATAL MECHANICS
Authors: Aylor Donald E. , Parlange Jean‐Yves , Krikorian A. D.
Published: January 2018

A model of stomatal movement due to changes in turgor is presented which systematically illustrates the role of certain anatomical features. During the expansion of paired guard cells, there are two physical constraints that cause the guard cells to bend and thus open the stomatal pore. The radial orientation of the micellae is shown to be the crucial feature which directly transmits the movement of the dorsal wall of the polar and central section to the stomatal slit. Furthermore, it is necessary that either the overall length of the entire stomatal apparatus or length of the common wall between the polar segments of the guard cells be constrained during the expansion of the guard cells. The model also shows that asymmetrically thickened guard cell walls are not necessary to cause bending of the guard cell. The ideas set forth in our model are consistent with the opening movements of both elliptical and grass‐type stomata.
MIGRATING CAMBIAL DOMAINS AND THE ORIGIN OF WAVY GRAIN IN XYLEM OF BROADLEAVED TREES
Authors: Hejnowicz Z. , Romberger J. A.
Published: January 2018

Anatomical analysis of wavy‐grained xylem samples of Fraxinus, Acer, and Betula reveals a strong underlying pattern of orientational domains within the cambium. Domains are local areas in the cambium within which the orientation of pseudotransverse divisions of fusiform initial cells is predominately unidirectional rather than random. The orientation of ray splitting and ray uniting also tends to be unidirectional within domains. Because their boundaries migrate with time, domains are not fixed in shape or position. A specific group of initial cells may first be located in the interior of a domain, later near a boundary, and still later in another domain of opposite orientational prevalence. Domain patterns and their movements were delineated by classifying and mapping ray splitting and uniting events in temporal series of tangential sections of terminal late xylem. The domain patterns move slowly upward, preceding the similarly outlined, but noncoincident, grain pattern. A wavy grain pattern can be interpreted as being the result of a domain pattern of similar geometry. The efficacy of a domain pattern in eliciting a grain pattern is probably indirectly dependent upon the frequency of occurrence of pseudotransverse divisions and of ray splitting and uniting. The frequency is low in cambium producing straight‐grained wood. Evidence of 10‐fold and greater increases in frequency of ray splitting and uniting was found in straight‐grained to wavy‐grained transitional xylem.
THE VASCULAR TRANSITION REGION OF HELIANTHUS ANNUUS. I. BILATERAL AND UNILATERAL PATTERNS OF DIFFERENTIATION
Authors: Scheirer Daniel C. , Hillson Charles J.
Published: January 2018

The vascular transition region of Helianthus annuus L. may exhibit either a unilateral or a bilateral differentiation of primary phloem groups. The unilateral type of transition has been previously described but the bilateral type with its two variations is described here for the first time. The three patterns of transition are compared, and the significance of the variability of transition regions is discussed in terms of basic transition types and phylogenetic importance.
DIFFERENTIATION, ORGANOGENESIS, AND THE TECTONICS OF CELL WALL ORIENTATION. I. PRELIMINARY OBSERVATIONS ON THE DEVELOPMENT OF THE OVULE IN COTTON
Authors: Lintilhac Philip M. , Jensen William A.
Published: January 2018

This paper, the first of a series of three, raises the general question of the relationship between stress, organogenesis, and cell wall orientation in a growing structure. It outlines a short descriptive chronology of events in the prepollination development of the ovule in cotton and proceeds to a brief experimental comparison of nucellar development in tissue culture with and without integuments. The significance of the integuments as mechanical effectors is discussed in terms of stresses which they induce in the growing ovule.
GEMMIFEROUS FERN GAMETOPHYTES—VITTARIACEAE
Authors: Farrar Donald R.
Published: January 2018

Approximately 10 % of all fern species reproduce vegetatively in the gametophytic stage by means of gemmae. Gametophyte morphologies in these species depart radically from the commonly figured heart‐shaped type and expand considerably the opportunities for physiological and morphological studies utilizing fern gametophytes. Original observations on four species of vittarioid ferns are presented and compared with earlier observations on gametophytes of this family. Vittarioid gametophytes grow from a discontinuous marginal meristem which results in a much branched thallus of indeterminant growth. Aerial branches of the gametophytes terminate in gemma production, which proceeds by a regular and predictable sequence of events. The sequence may differ considerably among species but is remarkably constant within species. Archegonia are produced on short ventral branches, and antheridia are produced primarily on germinating gemmae. Ananthacorus angustifolius is the only known member of the Vittariaceae which does not produce gemmae and is considered to represent the primitive condition. In this species antheridia are scattered over the thallus, suggesting that a change in the mode of control of antheridium production may have evolved in the family along with gemma production.
FLORAL DEVELOPMENT OF POTAMOGETON RICHARDSONII
Authors: Posluszny U. , Sattler R.
Published: January 2018

The inception and development of the sterile floral appendages of Potamogeton richardsonii have been re‐investigated with a refined dissection technique (Sattler, 1968) and improved microtechnical methods (Feder and O'Brien, 1968). The results obtained by Sattler (1965) are confirmed, i.e., the sterile appendages are initiated at the flanks of the floral apex before the stamen primordia are formed. Consequently, they may be homologized with tepals or perianth members, although in the mature flower they are inserted at the stamen connective, due to growth between and at the base of each developing tepal and stamen. Each carpel arises as a radial primordium which becomes peltate immediately after its inception. One ovule primordium is initiated at the cross‐zone. The stigma becomes bilobed. A slight outgrowth develops at the abaxial side of the style. The floral apex has a two‐layered tunica. The primordia of the tepals, carpels, and ovules arise by periclinal divisions in the second tunica layer, whereas the stamen primordia are initiated by periclinal divisions in the corpus and second tunica layer. Variation in floral pattern, especially with regard to the number of appendages, has been observed in flowers near the tip of the inflorescence axis.
STRUCTURE AND DEVELOPMENT OF SIEVE ELEMENTS IN THE LEAF OF ISOETES MURICATA
Authors: Kruatrachue Maleeya , Evert Ray F.
Published: January 2018

Leaf tissue of Isoetes muricata Dur. was fixed in glutaraldehyde and postfixed in osmium tetroxide for electron microscopy. The very young sieve elements can be distinguished from contiguous parenchyma cells by their distinctive plastids and the presence of crystalline and fibrillar proteinaceous material in dilated cisternae of the rough ER. During differentiation, the portions of ER enclosing this proteinaceous substance become smooth surfaced and migrate to the cell wall. Along the way they apparently form multivesicular bodies which then fuse with the plasmalemma, discharging their contents to the outside. At maturity, the sieve element contains an elongate nucleus, which consists of dense chromatin material, and remnants of the nuclear envelope. In addition, the mature sieve element is lined by a plasmalemma and a parietal, anastomosing network of smooth ER. Both plastids and mitochondria are present. P‐protein is lacking at all stages of development. Tonoplasts are. not discernible in mature sieve elements. The end walls of mature sieve elements contain either plasmodesmata or sieve pores or both, but only plasmodesmata occur in the lateral walls.
SCANNING ELECTRON MICROSCOPE STUDIES OF THE SPINES AND GLOCHIDS OF THE OPUNTIOIDEAE (CACTACEAE)
Authors: Robinson Harold
Published: January 2018

The genera of the Opuntioideae are surveyed for certain spine and glochid structures. Retrorse scabrosity of both spines and glochids is regarded as characteristic of the subfamily. Critical differences are noted in the bases of the glochids, flattened fish‐tail forms being found in Opuntia, Nopalea, Cylindropuntia, Tephrocactus, and Tacinga, and enlarged, rounded, hollow forms in Pterocactus and Grusonia. Small unflattened bases are found in Pereskiopsis and Quiahentia. Minor variations of the flattened form of glochid base are noted in Cylindropuntia, Austrocylindropuntia, and Opuntia brasiliensis; and the possible significance of the structures is discussed.