570 MONTHLY WEATHER REVIEW. AUGUST, 1919
dark mornings, it is es ecially difficult to ascertain either
a guess rather than wait to determine the true classifica- tion, yet it should be remembered that observations of this character areoften of less value than no observation
a t all and from a scientific standpoint are vicious in the estreme. tion and every well-determined direction of cloud move- ment is a distinct contribution to science and in this is its own reward.
the direction or kind o P c.loud, and many observers hazard Every careful, conscientious cloud ohserva-
FROST CONTROL AND RELATED FACTORS.
By J. C. WEITTEN, Profemor of Pomology, University of California.
[Dated February, 1919.1
Heretofore we have thought of protecting plants from cold only by direct methods, such as covering or shelter- ing the plants or by orcliard heat,inu, to raise the tem- perature of the surrounding a.tniospKere. This concep- tion was based upon the accepted belief that a given kind of plant inherits a given depee of hardiness; that there is a ''critical temperature,' above which the plant will live without injury and below which the plant will be injured or even die. Certain kinds of plant,s are notably hardy or resistant to injury .from cold. Others are notabl tender and subject to injury even in relatively
We now know that while the above factors are true, in part, they do not explain the whole truth in deteimining the resistance of a plant to cold or to drou ht or to heat
or op ose the health and safety of the plant. To enipha- size t 1 is statement we only need to call attention to the fact that a given variety of f!uit t1;ees niuy safely eiulurt! low winter temperatures while it is dorniai;lt or at rest: that it may be injured by a mere frost after it has st,artecl growth in vpring; and that a sudden frost may kill it after it has gotten into the accelerated growth of the warmer sumnier. The state or condition of a plant a t a given.tiiiie, its degree of ripeness and rest, or it,s dogree of actmity and growth governs largely how much cold or other unfavorable influence thf tree may safely endure. Studies made a t the Missouri Esperimen t Station show that normally the sap of a fruit tree is least concentrated (contains the least sugar a.nd digested plant food) during the period of rapid length growth in spring and ea.rly summer. Sap becomes more and more concentrated after len th growth ceases. The supply of plant food reserves %ecomes greatest as the tree goes into winter condition. The earlier a tree finishes its len th growth the niore
supply of plant food reserves. The more concentrated its sap the more cold the tree will stand either in wiliter
mild c Q imates.
or to any other environmental influence t E a t may favor
concentrated its sap becomes and t h e more abundant its
In t,he new systeni of pruning the main limbs arc est.ablished as early as possible. Once they are est.ab- lislied they are not subsequently headed back. They are pruned by thinning out surplus limbs. Length growth ceases early. The tree early attains a concentrated sap and stores plant food reserves. These slow-growing limbs nnd leaves become firm in testure a.nd evaporate hut libtle water. There is no rank succulent upper limbs t.o rob or shade out the parts below. The leaves a.re not likely t.0 draw water out of tlie fruit in time of tlrouuht. The concentrated sap gives up its water less read2y. Such trees will endure more spring frost or
mom drought, due to their better ripened or perfected tissue and their inore c.oncentratec1 sap.
any surplus tender, sncculrnt water sprouts that are rowing where they are not wanted. Any permanent knhs that are cont.inuing 1engt.h growth too late may be chiecked in their growth by clipping them hack. Dead. broken, or diseased parts should he removed.
So long as trees can secure ample water t.o supply their leaws, it is not desirable to reduce tlie leaf surface more than to check length growth of late-growing limbs. If droxght is severe and trees are evaporating more water t h i can be supplied, evaporating surface may be re-
cluced by judiciously renionn the more tender, succulent
tree. Tender, soft, new leaves evaporat,e many times more water than older, firmer leaves t.ha.t formed early in t.he season. The older, firmer leaves, if healthy, and which take on a dark green color, are niore s?rvicea.ble in the elaboration of plant food reserves.
Judicious summer pruning consists of t,he removal of
parts, which are least needec f as permanent, limbs of the
WHITEWASH THE TRUNKS OF YOUNG TREES TO PREVENT
SUN SCALD.
The trunks of young trees should be whitewashed as
so011 as they arc. planted in t,he orchard to prevent sun scald and tlie drying out of t,he buds and rowin layer. Whitewashing the trunks of young trees s%ould [e ke t up each winter for the first three to five years after t E e
young trew are planted. Exposed trunks or hare main limbs of older t,rees ai- also protected from sun scald if kept whitewashed.
Sunscald is most seven in winter, even though the injury may not be noticeable until summer. The coloring matter in the hark of trees ahsorbs heat enough from the sun's raj- on sunny days to raise the temperature of the growing layer to from 15' to 35' (F.) above the temper- ature of the air. This renders the cells of the growing layer and buds, especially on the sunny side of t.he tree, turgid, active, and tender.
As the sun goes down at night, t.he temperature of the tree falls prom tly to the temperature of the air, This wide fluctuation of temperature between clay and night in- jures the growing layer and buds.
which may be to P reezing or even below.
AUGUST, 1919 MONTHLY WEATHER REVIEW. 571
Whitewashin the exposed trunks reflects the suns
temperature. This keeps the tissues of the tree dormant, even during a sunny day, and not subject to injury when the temperature drops gradually at night. Heretofore i t was thought that sun scald occurs duriiq the hot dry days of sumnier. A study of the tempera- ture of the trunks and twigs of the trees during sunmier shows that this IS not the case. The upward assage of cool water from the roots and
of the tree above ground. Duiiiig a hot, dry dity in summer the triink and twigs of a tree are usually cooled to a temperature from 1.5 to 20 below the temperat-ure
of the air. This cooling is most ninrked adjacent to green leaves, which evaporate much water. It is least marked on long, hare trunks and main liml,s which have no twigs and leaves to evaporate water. This emphasizes the de- sirability of preseiving rosettes of leaves and short fruit- ing twigs all u and down the trunks and niain limbs to shade and coo f the parts where sun scald usually occurs. It also emphasizes the desirability of low-headed trees.
rays, keeping t % e tree a t or a little below atmospheric
i t s evaporation P rom the twigs and leaves cools the parts
These leaves also digest plant food to nourish the limbs, trunks, and roots. maintaining a thicker, healthier annual ring of new sap wood. If sun scald begins on the soUtah side of the trunk and main limbs in winter, it cnn continueduring summer. Winter sun scald dries out the tissues and opposes the development of sap wood and green leafy twiw on the esposed parts. Cool sa is not readily Carrie8 through these driecl and injure (P parts so they are less cooled during hot summer dar.. A good whitewash w ich will stick may be made as fol-
the lime is slack- on the salt and sulphur so as to forni a wash which will stick. Add water to make a thick whitewash and apply to the tree trunks by nicans of a spray pump or a brush. Whitewashing the trunks of young trees or sun- scalded parts of older tree.8 is desirable, espec.ially in winter. It is not necessar on older trees with thick bark
2 pounds of salt
and which possess twigs t t a t shade the limbs.
ABSTRACTS, REVIEWS, AND NOTES.
BRITISH RAINFALL ORGANIZATION.
On Julv 35, 1919, in ncrordancc with m wrangernent approved by H. M. Treasury, the respoiisilility or t,he mana ement of the British rainfall orgitnization was
trans P; erred by the trustees of the organization t,o the director of the meteorologicnl ofice. In accorilanre with the terms of the transfer, the pul-,licution of Bri&is?i Hahi.- fa8 will be continued and Synioiess Metcoroloqital .&gar
d n e is also assured of continuance in association with the (;ircular of the Me t.eorologica1 Office. The news of the retirement of Dr. H. It. Mill on accwunt of his impaired eyesight was recently announced, a d has been received with much regret hy all who are interested in the study of rnin!till. Tne 19 yeuis d his connortion with the organization have shown continuous develop- ment of the sttidy of the suhject on scientific linea.- .,Weimrologi.cd O#cc C.rc-uZa.r, 30, 8cpt. I , 1919, 1 3 . 1.
THE METEOROL001CAL GLOSSARY * OF THE BRITISH METEOR bOG ICAL OFFICE.
The title of tlh esceedingly useful conipend is some- what misleading. It is really a pocket encyclopsdia of meteorolo y and kindred sciences. The name glossary suggests t f a t one may find here definitions of at least all the more usual words and expressions pertaining to meteorology, but such is not the case. No meteorolo ical
lhe lista of definitions found in Bartholomews Atlas
of Meteorology and Marriotts  Hints to Meteorologic.al Observers supply even less ade uately than the new
information needed by nieteorologis ts. Only about 400 terms or subjects are treated in the work under review. Taking the letter A as a sample
of the book in eneral, we note the omission of ajterglow,
arched squull, and atmometer (atmidometer), besides hosts of rarer ex ressions belongin to the lan uage of nieteor-
glossary worthy of the name has yet been.publis % ed.
publication of the Meteorological 8 ffice the lexicographic
airdrainage, A 5 penglow, anchor-ice, anomaly, untitrade,
ology, suc! as advection, uelfoscope, 30 f us, aerobioscope,
1 Great Britain. Meteorologicaloffice. Metmlogiealglossary. 4th issue. London. 1918. 358 p. 24.. (M. 0.2% 11.)
140822-1-
aerocl.inoscope, aeroconiscope, aeroscope, aerotlmin, a?tAri- oxcope, air-tester, All-Hallown summer, allobar, ammil, etc. The size of the iueteorological vocabulary is realized by vsry few met,eorologists. The present reviewer has labored desultorily during the past 10 years in gathering material toward a comprehensive meteorological dic- tionary, iiicluding in its scope both scientific and non- scientific tems relating to weather and climate, and although upward of 10,000 term have already been listed the enumeration iY still fra=mentary. While the glossary of the Meteorological Office contains many definitions, i t is primarily a series of articles, some of them several )ages in length, on topics that either are
ological application. Under the latter headwe find several physical and mathematical articles of rather exceptional interest to the meteorologist, to whom they su ply information not easily obtainable elsewhere in a krm so convenient for his use. There are, for esaniple, escellent brief discussioiis of harmonic analysis, correla- tion, heat, entropy, and buoyanc .
the fruit of the latest investigations, and are therefore a
valuable and indispensable sup lenient to all esistin
represented, and there are succinct presentations of recent views aud data relating to such topics as the audibility of explosions, visibility, gusts, eddies, and gradients.
The definitioiis of terms are generally valid and accu- rate, though a few are open to improvement. We regret to find that British meteorologists persist in using the word isopleth (p. 168) as a synonym of isogram, the generic name for the %o- lines. Ever since the former term was introduced by Ch. Vogler, in 1877, it has been applied almost exclusively, outside of recent British writings, to an isogram drawn on a system of coordinates a t least one of which indicates time rather than space. Isograms of this class are described by Hann, in his Lehrbuch der Meteorolo e, 3d ed., p. 91, and in this connection he says: Der % anie Loplethen, der eigent- lich Kurven gleicher Zahlenwerte beteutet, was a auch
directly nieteoro \ ogical or have some important meteor-
The articles on purely meteor0 T ogical subjecta represent
K textbooks of meteorology. Aero P ogical subjects are we
z. B. die bothermen usw. sind, wird nur au diese b arsteb Zungsmethode angewendet. (Our italics.) I he important