bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE PROBLEM OF GRAFT HYBRIDS AND CHIMAERAS
Authors: WEISS. F. E. 
Published: January 2008

Summary.In the introductory paragraphs of this review, the question was discussed whether after grafting, any effect of scion on stock or vice versa was known to occur. It was indicated that apart from the infectious chlorosis, a supposed virus disease, any influence of stock on scion or scion on stock is generally regarded as nonexistent. Professor Daniel, however, who has had unrivalled experience of grafting, holds the opposite view and believes strongly in the intermingling of characters of stock and scion (hybridation asexuelle) caused particularly by his method of mixed grafting.The earliest graft hybrid which has been scientifically investigated, the so‐called “Bizzarria” Orange, is then described. It is regarded by some as a true graft hybrid, by others as a synthetic chimaera of periclinal constitution. Other instances of sectorially diverse oranges may be due to partial segregation of heterozygous forms of Citrus.The well‐known and much discussed Cytisus Adami seems according to the investigations of Buder (1910 and 1911) to be what Baur (1910) has called a periclinal chimaera with a core of the Common Laburnum surrounded by an epidermal layer of Cytisus purpureus.Though according to Baur (1919) and Meyer (1915) the Crataegomespili are also periclinal chimaeras with a core of the hawthorn surrounded by one or more layers of the medlar, the more recent investigations of Haberlandt (1926) and Weiss (1925) as well as previous observations by Daniel (1914) throw some doubt on the chimaeric structure of these so‐called graft hybrids.The constitution of Pirocydonia is still uncertain and the Amygdalopersica described by Daniel (1914) seems likely to be a heterozygous plant.Of the various forms of growth obtained by Winkler by grafting tomato on nightshade stock and vice versa, four seem to be definitely proved to be periclinal chimaeras, but the constitution of Solanum Darwinìanum is still doubtful, and it may possibly be a true graft hybrid formed by a union of vegetative cells.The formation of chimaeric growths of variegated plants both of sectorial and periclinal constitution was experimentally established by Baur (1909) for Pelargonium and further investigated by Bateson (1919 and 1920), Chittenden (1925) and others. This has led to interesting discussions and observations concerning the part played by the plastids in the reproductive processes of plants and generally in the inheritance of variegated leaves.A further point of interest is the suggestion made by Chittenden (1930) that certain eversporting forms of flowers may be of chimaerical constitution.
THE RESPIRATION OF INSECTS
Authors: WIGGLESWORTH V. B. 
Published: January 2008

SummaryThe review covers the ground of external and internal respiration in insects, but deals neither with quantitative changes in metabolism, nor with the intimate processes of oxidation in the tissues.The general anatomy and histology of the tracheal system are described. The form of the tracheae and their mode of ending in the tissues is extremely varied in different insects and in different organs. The question whether the tracheal endings contain fluid or air and the problem of what forces keep the larger branches filled with gas are discussed in detail. The embryological development of the tracheal system and the nature of the “spiral thread” are briefly considered.The exchange of gases in the tracheal system is effected primarily by diffusion. This is modified by opening and closure of the spiracles (“ diffusion control ”) and by mechanical ventilation of the larger tracheal branches (“ventilation control ”). The mechanism of tracheal ventilation is discussed at length: including the part played by the air sacs and the question whether there is a directed stream of air through the tracheal system.The respiratory movements are controlled by nerve centres, variously situated in different insects; and these centres may be stimulated either by oxygen want or by carbon dioxide excess.The relative importance of the spiracles and the skin in respiration, especially in the elimination of carbon dioxide, is discussed.Under the respiration of aquatic insects the functions of the “blood gills,”“tracheal gills ” and “ cuticular gills ” are reviewed, and the problems connected with the “ hydrofuge ” structures of aquatic insects and the air stores which they carry are considered. The respiration of parasitic insects presents many parallels with that of aquatic forms.The part played by the blood of insects as a carrier of oxygen is discussed in detail.
THE DERMATOPHYTES
Authors: GREGORY. P. H. 
Published: January 2008

Summary.The dermatophytes are a group of fungi which parasitise animals by invading the keratinised portions of the epidermis. They appear to be unable to attack internal organs and are apparently dermatotropic. Ringworm in its various forms is a primary localised dermatophyte infection.The concept of the activity of the dermatophytes has been enlarged by the recognition that they can also determine secondary non‐parasitic skin lesions on distant parts of the body. Several records of isolations of these fungi from the blood indicate that spores may be carried from the primary lesion to other parts of the body by means of the blood stream.Hairs infected by certain species of dermatophytes show a green fluorescence in ultra‐violet light not possessed by uninfected hairs. This phenomenon can be utilised to detect infected hairs among normal ones. The fluorescence is due to a water‐soluble substance which can be extracted from infected hairs.The wealth of spores and other organs produced in cultures on certain animal and vegetable media suggests that these fungi have a natural saprophytic stage in their life history. It is also possible that the saprophytic stage occurs on naturally infected hairs after they fall from the animal body.The dermatophytes in culture are subject to variation. The particular irreversible degenerative mutation known as “pleomorphism” can take place in isolates derived from either a single aleuriospore or a single fuseau. Pleomorphism appears to be due to a toxic action on the organism of monosaccharides and disaccharides. In media containing polysaccharides pleomorphism is not observed.Asci have been reported by several workers. While certain of these records appear to be unsubstantiated, others point to an affinity between the dermatophytes and the Gymnoascaceae. The classification of the 200 or more species is in a state of chaos. The newer systems show few advantages over Sabouraud's revised classification.
THE RETENTION AND PHYSIOLOGICAL ROLE OF UREA IN THE ELASMOBRANCHII
Authors: SMITH. HOMER W. 
Published: January 2008

Summary.The high urea content (2·0 and 2·5 per cent.) that characterises the blood, body fluids and tissues of the Elasmobranchii owes its origin to the relative impermeability of the gills and integument to this substance, and to the circumstance that the urea is actively conserved by the elasmobranch kidney.In consequence of this physiological uraemia, the elasmobranch is osmotically superior to its environment, even in sea water, and is able to absorb at least a minimum quantity of water for the formation of a urine that is isotonic or hypotonic to the blood, in accordance with the osmotic limitations of the fish kidney.We may suppose that the uraemic state tends to develop and to be regulated more or less automatically; urea is constantly being formed by the ordinary metabolic combustion of protein; water shortage leads to oliguria and urea retention, and the accumulated urea in the blood raises the osmotic pressure of the latter to a point where water is again available by direct absorption. Water plethora (as in fresh water) leads to diuresis and increased urea excretion, which in turn lowers the osmotic pressure of the blood and in some measure, at least, reduces the rate of water absorption.Trimethylamine oxide, which imparts about one‐quarter as much osmotic pressure to the blood as does urea, is also conserved by the elasmobranch; the fact that this substance is present in the urine in lower concentration than in the blood suggests that, like urea, it is actively reabsorbed from the glomerular filtrate.This physiological uraemia is apparently an archaic biochemical habit acquired early in elasmobranch evolution, since it is shared by the divergent orders of the subclass. Presumably it is a secondary mode of osmotic regulation superimposed upon the more primitive one of branchial regulation, as observed in the teleostomes.The cleidoic egg, unique (among the fishes) in the Elasmobranchii, and the viviparous mode of reproduction, are viewed as adaptations to urea retention, protecting the embryo against the loss of urea during its early development.Urea retention enables the Elasmobranchii to maintain a considerably greater rate of urine formation (water excretion) than is observed in the marine teleosts, a fact that perhaps explains why the former do not show the glomerular degeneration or the aglomerular development observed in the latter.Whereas urine formation in the marine teleosts appears to be carried on normally at a reduced level considerably below the maximum possible rate, the elasmobranchs appear to maintain a maximal (though small) degree of glomerular activity at all times. Unlike the teleosts, they appear to possess no mechanisms for reducing glomerular activity; it may be that because of their superior osmotic position, due in turn to their physiological uraemia, they have never been faced with the necessity for conserving water to an excessive degree in the kidneys, and have therefore never evolved the means for doing so.
GENETICS IN ITS APPLICATION TO PLANT BREEDING
Authors: HUDSON P. S. 
Published: January 2008

SUMMARY

The importance of Mendelism in relation to practical breeding problems is illustrated by reference to early work on the inheritance of economic characters.
Examples are given of improved varieties that have been produced by individual plant selection. The possibilities of success are shown to be dictated by the completeness of the material and one of the essentials for successful breeding is shown to be the collection of adequate and representative stocks of initial breeding material. This is illustrated largely by reference to Russian work, which has also elucidated the laws governing the distribution of plant varieties, characters and genes.
The possibilities of putting interspecific or distant crosses to practical use are analysed and cases where this has been done are cited. Chromosome duplication is shown to be a frequent phenomenon in such cases and to be a factor greatly increasing the economic value of such distant crosses. Numerous cases are quoted and the phenomenon is shown to have played an important role in the origin of new species and forms in nature. Its experimental control is thus of great practical value.
The origin of new forms of pathogenic fungi by hybridization and mutation is illustrated and shown to be a serious obstacle in breeding for disease resistance.
Examples are given where the obstacle has been overcome by breeding methods and other cases are mentioned where the problem of disease resistance remains unsolved.
The role of mutations in the origin of new forms of agricultural plants is discussed and the possibilities of effecting this process artificially are analysed.
The phenomenon of vernalization is described, with special reference to breeding. The significance of this and other recent physiological studies in producing forms possessed of earlier maturity is discussed.
The nature of plant yield is discussed and reference is made to attempts to analyse and regulate this by genetical methods.
BIOCHEMISTRY OF THE LOWER FUNGI
Authors: BIRKINSHAW J. H. 
Published: January 2008

SUMMARY

The study of the biochemistry of the lower fungi received a great impetus from the classical researches of Wehmer begun in 1891. The more recent developments are here reviewed. The biochemical characteristics of moulds often correspond closely with the taxonomic features and thus assist in classification.
A medium suitable for mould growth must contain the elements sulphur, phosphorus, potassium, and (probably) magnesium. Traces of certain heavy metals, namely iron, zinc, copper, and manganese, seem to be essential for the growth of Aspergillus mger and probably of other moulds.
Combined nitrogen is also essential for growth and may be supplied in inorganic or organic form.
The possible sources of carbon are very diverse, alcohols, carbohydrates and many organic acids being readily utilized.
Although moulds are essentially aerobes, some species can tolerate a low oxygen tension. Diminution in the oxygen supply may alter considerably the products of metabolism.
Small amounts of certain organic substances specifically stimulate or inhibit some of the metabolic processes of moulds. Vitamins of the B group have a favourable effect on growth and sporulation in the case of some species. Certain moulds are able to elaborate substances inhibitory to other micro‐organisms.
The metabolic products are very varied in nature and range from the simpler plant acids (oxalic, fumaric, malic and citric acids), polyhydric alcohols and products of alcoholic fermentation to substances containing non‐benzenoid rings such as derivatives of furane, pyrone, tetronic acid and cyclopentanone, substances containing benzenoid rings, such as derivatives of benzene, benzoquinone, anthraquinone and xanthone, pigments, sterols, fats, phospholipins and complex polysaccharides. Vitamins of the B group and the provitamins A and D are also found amongst mould products. In presence of arsenic, certain species such as Scopulariopsis brevicaulis produce volatile organic arsenical compounds. Substances containing chlorine as part of the organic molecule are also synthesized from inorganic chlorides, and organic nitrogenous compounds including proteins from inorganic nitrogen. Evidence is thus afforded for the outstanding synthetic activities of the lower fungi.
Whilst the mechanism of synthesis is as yet an unsolved problem, the suggestion is advanced that some of the complex products may arise from the polysaccharides which are of such frequent occurrence in mould metabolism.
PROPERTIES OF THE CELL SURFACE
Authors: HARVEY E. NEWTON , DANIELLI J. F. 
Published: January 2008

SummaryMeasurements of the tension at the cell surface show that the tension lies between 1·0 and 0·1 dyne. The results of measurement of the tension at simple oil‐water interfaces are discussed in relation to this and it is shown that a simple lipoid layer is not sufficient to explain the low tension at the cell surface; the low tension must be brought about by the adsorption of protein upon the lipoid surfaces. This gives rise to a picture of the cell surface which involves, as a minimum, a bimolecular layer of lipoid molecules between two layers of protein molecules. Measurements of the thickness of the plasma membrane, of its permeability and wetting properties, are found to be compatible with this model. The acidic groups of the protein and lipoid can react with cations to give a sodium‐calcium antagonism. The membrane permits preferential penetration of lipoids, and at the same time offers a physical basis for pore and mosaic effects. High temperature coefficients of penetration are found to be explicable by a simple physical mechanism. It is shown that by variation of the pH of the external medium it is possible to distinguish between three possible mechanisms for ionic penetration; in the case of the erythrocyte the mechanism appears to be simple diffusion through a lipoid layer. The wetting properties of the plasma membrane also indicate that it is fatty in character, and that, in the case of Arbacia eggs, the pellicle is liquid.It is concluded that the structure of the plasma membrane must be similar to that suggested as a minimum possible structure.
THE FINE STRUCTURE OF BIOLOGICAL SYSTEMS
Authors: PICKEN L. E. R. 
Published: January 2008

Summary1. Present‐day interest in the study of fine structure may be traced back to the work of the botanist, Carl Nägeli, to whom the conception of the micell is due.2. The continuation of Nageli's optical studies of biological structures, the development of X‐ray analysis, and the investigation of the properties of long chain high polymers, have led to the extension and modification of Nägeli's ideas.3. Two main types of molecular aggregate are of particular importance in biological systems—linear (or fibrous) and laminar structures. These may be classified as subcellular, extracellular and supracellular.4. The subcellular structures which have been examined include: protein fibres from the sap of virus‐infected plants; chromosomes; asters and spindles; and contractile fibrils (muscle fibrils, myonemes, pseudopodia and cilia). These all appear to be composed of chain molecules arranged approximately parallel to the long axis of the structure in question.Laminar subcellular structures include the surface membranes of animal cells (nerve fibres, echinoderm eggs, red blood corpuscles) and the outer portion of the rods and cones of vertebrate retinae. These are composed apparently of alternating layers of protein and lipoid molecules.5. Extracellular fibrous structures are represented by elastoidin, collagen, elastin and chitin; laminar structures by the keratinous egg cases of selachians, the cellulose test of tunicates and chitinous integuments in general. The relation of these to other natural and synthetic high polymers is discussed.6. The category of supracellular Structures, that is, of macroscopic fibrous or laminar structures of multicellular origin includes (a) hair and muscles, and (b) enamel and bone.7. It is clear that a close parallel in structure and behaviour exists between biological materials and high polymer substances. The morphological implications of this parallel are discussed and the importance of molecular morphology for the biologist is considered.
THE GENETICS AND CHEMISTRY OF FLOWER COLOUR VARIATION
Authors: LAWRENCE W. J. C. , PRICE J. R. 
Published: January 2008

Summary1. The principal flower colouring matters are the anthocyanins, anthoxanthins and carotinoids. Variation in colour depends upon the presence or absence of one or more of these substances, upon structural alterations in their molecules, changes in thep pH of the cell sap, or quantitative changes affecting the amounts of pigment produced.2. Pigment production is genetically controlled, and in a number of cases complementary genes are involved.3. Variation in the amount of any pigment is also gene controlled. Such quantitative differences can be interpreted in terms of the velocity of the reactions involved in pigment production.4. Modifications of the chemical structure of anthocyanins, including the state of oxidation, glycosidal type and probably the degree of methylation are each determined by simple gene relationships. In certain cases reactions are incomplete, giving rise to mixtures of anthocyanins.5. The synthesis of anthocyanins in the plant is correlated with that of anthoxanthins. Some workers consider that the anthocyanins are formed from flavones or flavonols, but the most comprehensive theory, put forward by Robinson, postulates parallel formation of anthocyanin and anthoxanthin from the same intermediate. On this theory cyanidin and quercetin are synthetically the simplest members of their classes, others requiring additional stages of oxidation or reduction. The above view is supported by statistical analysis of the distribution of anthocyanins in flowers, fruits and leaves.6. Heritable chemical differences result in the first place from gene action. They may be accentuated or minimized by gene interaction, which can modify dominance relationships and is sometimes the causal factor of epistasy. A study of gene interaction can also help in the determination of the sequence of gene action.
THE CRITERIA OF PURITY USED IN THE STUDY OF LARGE MOLECULES OF BIOLOGICAL ORIGIN
Authors: PIRIE N. W. 
Published: January 2008

SummaryThe limits, in weight and chemical stability, of the group of substances referred to as large molecules are discussed and the range is arbitrarily taken as from particles unresolvable by the microscope to those with molecular weight 5000. A unit of molecular weight is proposed and its advantages are discussed in cases where the nature of the bonds holding a particle together is uncertain.Four distinct meanings that can be carried by the word pure are described, and examples are given of each type of purity.The types of observation generally made and presented as evidence that a substance is pure are considered under seven headings. Chemical analysis and crystallinity are the least reliable, and specific serological tests can only show the absence of contaminants whose presence is suspected. The measurement of end‐points, whether by serum precipitation or infection, is subject to several errors and can at best only indicate whether or not the major constituent of a preparation may be serologically active or infective.Electrophoresis, ultracentrifugation and studies based on the principles of the Phase Rule, i.e. solubility and partition measurements, give the most reliable evidence of purity at present available. Several reasons are given for thinking that even these methods may be fallible.
THE FUNCTION OF PHOSPHATE IN CELLULAR ASSIMILATIONS
Authors: M. KALCKAR H. 
Published: January 2008

SummaryTwo different types of carbonyl oxidation exist:(I) Carbonyl + HaO + pyridine‐enzyme← carboxylate + reduced pyridine‐enzyme.This type of oxidation is practically irreversible and consequently liberates a large amount of free energy. The normal redoxpotential of this system is extraordinarily low, i.e. carbonyl is a very strong reducing agent.(2) Carbonyl + phosphate + pyridine‐enzyme← carboxylphosphate + reduced pyridine‐enzyme.This type of oxidation is reversible and the change in free energy accordingly very small, which means that the normal redoxpotential of the system: carbonyl + phosphate ← carboxylphosphate + 2←+ 2H+ is very close to that of the system: pyridine‐enzyme ← reduced pyridine‐enzyme + 2←+ H+.Thus replacement of water by phosphate in the carbonyl oxidation eliminates a great fall in free energy by transforming the labile carbonyl into an equally labile acid anhydride, carboxylphosphate.The degradation of the polyalcohol structure of the sugar acid (glyceric acid) to the α‐keto acid structure of pyruvic acid releases a considerable amount of energy.Moreover, in this case the energy is directed and preserved by means of a phosphorylation.I am indebted to Dr D. M. Needham (Cambridge) for her generous help in preparing the manuscript for publication and to Prof. C. F. Cori, Dr G. T. Cori and Mr S. P. Colowick for their valuable and helpful suggestions.