the descriptive matter often a deftness of touch which is altogether delightful. This is a "popular" work; but it suffers from none of those elements of vulgarization that too frequently creep into the "popuar science" writing of this day. It is a book to be heartily commended to the teacher who strives for scrupulous accuracy in the non-mathematical presentation of scientific things.

The publisher says on the jacket of the book that it contains "the largest and finest collection of cloud photographs ever presented in one volume." One must express surprise at this encomium. The illustrations are good, on the whole; some of them are very good; a scant few of them possess the almost stereoscopic loveliness in the halftone rendering of form and depth and distance, which is an outstanding characteristic of some recent foreign cloud books.

The clouds presented as types are in a few cases disappointing. It would be difficult indeed for all to agree on the choice of the picture intended to illustrate a given type. For instance, Figure 33, "Stratocumulus, Roll Type," seems to the reviewer to present nothing more than a good cumulus cloudscape with the usual receding glimpses of the bases of ever more distant clouds. The well-formed cumuli in the nearer distance appear to indicate that conditions weren't right for roll-type cumuli just then. The strato-cumulus in Figure 34, on the other hand, could scarcely be finer. Figure 41, "Cumulus," pictures very prettily the grounds of the U. S. Department of Agriculture in Washington. In Figure 42 the sky is quite too crowded with irregularly disposed cumulus bases to leave any just impression of the en echelon arrangement it was desired to portray.

Such comments relate after all, however, to failings which are not of major importance. One will have to go far to find a volume more serviceable to its purpose, or better adapted to making us familiar with the names and habits and vagaries of form of these transient visitors to our skies.

be observed was the darkening of the plumage in such pigmented races as Rhode Island Reds, Barred Plymouth Rocks, Silver Campines and Brown Leghorns.2 The addition of desiccated thyroid to the dietary of growing chicks, and the parenteral injec tion of thyroxin itself, led quickly to an increase both in quantity and extent of plumage melanins. This not only revealed a definite influence of the thyroid hormone on melanin production in these birds, but suggested a possible means of exploration by thyroxin of the pigment-forming mechanism itself, not only in birds but in mammals as well.

Accordingly, experiments were begun on several color varieties of mice and rats. Representatives of six varieties of mice, namely, piebald, pink-eyed, chocolate, dilute chocolate, dilute black and albino, and one variety of rat, namely, dilute black-hooded, received systematic abdominal injections of thyroxin. The dose for all ages was approximately 1 mgm. of thyroxin to every 500 grams of body weight, administered at intervals of three or four days. Interest centered chiefly about the behavior of naked or nearly naked young, to which thyroxin could be given as the coat developed from birth onward. When adults were given thyroxin, a patch of hair was clipped from the rump in each case.

In sharp contrast with the response of the domestic fowl, the administration of thyroxin under the conditions of the experiments produced no effect whatever on the coat color of the rats and mice, young old. The facts will be sufficiently established by a brief review of four typical experiments.

and

30

Results as in preceding cases.

Injections discontinued.

This failure of the mice and rats to respond to thyroxin indicates a marked difference between the mechanisms involved in feather and hair pigmentation in the birds and mammals observed. Large amoebid melanophores play a peculiar and conspicuous rôle in the development and distribution of feather melanin, a process that appears to have no counterpart in the developing hair. It is unlikely, however, that this or any other such histological difference is of fundamental importance in this connection. The simplest assumption to account for the observed facts is that these unresponsive varieties do not possess the factors essential, with or without thyroxin, to a deepening of their coat color beyond its typical limit. Dilute chocolate and dilute black do not appear merely as less intense color varieties of chocolate and black respectively, but differ from the latter in the absence of factor or factors necessary to the production of their characteristic coloring. The result of the physiological test with thyroxin thus accords with the well-known facts of their genetic behavior and current conceptions of their genetic constitution. HARRY BEAL TORREY

ON THE VELOCITY OF SOUND THE velocity of sound as a function of tube diameter has received consideration from time to time. Helmholtz, in 1863, proposed, without demonstration, the following as the governing relative,

V=V. (1-V)

where V, is the velocity in free air at 0° C., d is the diameter of the tube, n the frequency and e a constant. Later Rayleigh derived this relation from certain dynamical considerations but the experimental support for it has been meager and not satisfactory, due to lack of sufficient accuracy in velocity measurements.

Some years ago, Wold carried out some measurements by a method illustrated in the figure. Soundwaves from a tuning-fork or diaphragm at S travel down tubes T, and T, of variable length. The waves

A,

A,

are picked up by receivers R, and R, of the condenser transmitter type. The outputs are amplified by six stage amplifiers A, and A, and impressed on

the orthogonal pairs of plates of a low voltage Braun oscillograph tube. The Lissajous figure resulting can be brought to a straight line by adjustment of one of the tubes. If now one tube is gradually changed in length through one wave-length, the figure will pass through its elliptical cycle back to a straight line. This method of finding wave-length has shown itself capable of a surprisingly high degree of accuracy.

Recently, we have repeated the work with refinements as to frequency and temperature control and corrections for humidity. The attempt has been made to reach an accuracy of one part in ten thousand, but this has not been attained as yet, probably due to the effects of reflected components of the waves within the system. These have been greatly reduced but not entirely eliminated. The results thus far obtained, using brass tubing, seem to confirm Helmholtz's relation and are best represented by the following:

WATER TRANSLOCATION IN YOUNG
FRUITS1

IMMATURE Succulent fruits are essentially masses of meristematic tissue, although most of the protoplasts contain well-defined vacuoles. Their cells are everywhere in contact with neighboring cells, without interruptions by intercellular spaces. Almost universally these cell walls contain pectic (or related) substances which possess marked imbibitory properties. The purpose of this note is to emphasize a consequence of these conditions which is generally overlooked, namely, the importance of these hydrophilic layers in the translocation of water through the tissues. Our observations make it apparent that imbibed liquid passes over the surfaces of these cells, as well as through them by osmosis. The fibrovascular bundles furnish channels by which water and dissolved substances may enter the fruit, but the majority of the cells are at some distance from the ultimate divisions of the bundles. Liquids such as those found in young fruits will not readily diffuse through protoplasts, but they will pass through the pectose layers by imbibition.2

1 Paper No. 170 University of California, Graduate School of Tropical Agriculture and Citrus Experiment Station, Riverside, California.

2 Tupper-Carey, R. M., and J. H. Priestley. "The Composition of the Cell Wall at the Apical Meristem of Stem and Root." Proc. Roy. Soc. London B. 95: 109-131. 1923.

The

The tissues of the young fruits which we have examined are composed of parenchyma cells without intercellular spaces. Unchanged cellulose is found in the walls of these cells, especially in the peripheral regions, though in the deeper lying layers the cell walls frequently do not show the cellulose reaction. When sections of fresh material are treated with ruthenium oxychloride solution the cell walls become deep pink, thereby giving evidence of pectose. reaction is particularly strong in sections of the mesocarp of lemons, the endocarp of walnuts, the exocarp of apples, and the pericarp of tomatoes and of Carissa grandiflora. The thick walls of these cells may be readily seen in sections of fresh material if a proper mounting solution is used, but it is necessary to use a liquid which does not mix with water. We have used xylol. If the sections are in contact with an excess of water the colloidal layers swell to such an extent that their boundaries are indistinct. If they are mounted in 95 per cent. alcohol the water may be so completely removed from the colloidal layers that their true thickness is not seen.

The rate of water movement in these fruits seems fairly rapid and the fluctuations in size are in large measure dependent upon the amount of water held by the colloidal matter of the fruit. The distribution of water between the protoplast and its bounding wall doubtless is an expression of the equilibrium between the imbibitional power of the wall and the osiotic attraction exerted by the contents of the protoplast. When cell walls of wilted and turgid fruits are examined in xylol those of the wilted fruits show a marked decrease in thickness.

It is well known that the tissues of these and other immature fruits are rich enough in pectose to be valuable for the preparation of jellies and jams, but we wish to call attention to the occurrence of these

hydrophilic layers in the cell walls, and to emphasize their importance as paths for the translocation of water.

UNIVERSITY OF CALIFORNIA

H. S. REED

E. T. BARTHOLOMEW

3 Bartholomew, E. T. "Internal Decline of Lemons. III. Water Deficit in Lemon Fruits Caused by Excessive Leaf Evaporation." Amer. Jour. Bot. 13: 102

117. 1926.

MacDougal, D. T. "The Daily Course of Growth in Two Types of Fruit." Yearbook Carnegie Inst. Wash. 18: 69-70. 1919.

Haas, A. R. C. "Relation between Fruit Size and Abscission of Young Orange Fruits." Bot. Gaz, 83: 307-313. 1927.

The Antisterility Vitamine Fat Soluble E

By

HERBERT M. EVANS AND GEORGE M. BURR

with the assistance of

THEODORE L. ALTHAUSEN

Fifth and newest member of the Vitamine Family, and essential to the reproduction of higher animals!

In this monographic account of studies establishing the existence of VITAMINE E, 107 tables summarize an extensive experimental experience. Special characteristics or criteria for the determination of dietary sterility as due to VITAMINE E are clearly defined. For the first time there is given a thorough discussion and analysis of the vexatious phenomenon of initial fertility shown with many simplified diets and with supposedly E-free conditions. Hitherto unpublished also are the detailed accounts of the histopathology of the placenta in E-free gestation, of male sterility, especially of male behavior after destruction of the germ cells, and of particular steps in the isolation and concentration of the vitamine.

176 pages, quarto, illustrated, $5.00 postpaid

University of California Press

Berkeley, California

A Scrap-Book
of

Elementary

Mathematics

By

WILLIAM F. WHITE

A new edition brought out in response to many requests, containing notes, recreations and essays. A book interesting alike to students and teachers. Among the section headings are: A Few Numerical Curiosities, Miscellaneous Notes on Number, Familiar Tricks, Geometric Puzzles, Labyrinths, The Nature of Mathematical Reasoning, Alice in the Wonderland of Mathematics.

Price $1.50

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