available phosphate in certain Indian soilsat times only one fiftieth to one twentieth of the amount usually regarded as necessary for fertility-have been under investigation. So, too, have been the low values of available potash in certain other soils. In this connection efforts have been made not only to correlate potash-deficiency with disease in animals and plants, but also to utilize the ash of at least one proclaimed weed as a means of adding potash to the soil, and incidentally as a partial set-off against the cost of eradication. Botanical work has included, in addition to survey operations, much that is of immediate economic importance. One notable instance is afforded by the device of a method of selfing cotton, which is not only simple, but is also said to have proved successful. Much sound work has been done with indigo, jute, opium, rice, sugar and wheat on agricultural lines, and with grasses, as well as trees, on forestry lines.

On the physical side we find that researches in solar physics have included an investigation of the displacement of the lines given by the electric arc. This study has supplied interesting results, and led further to a determination of wave-lengths in the spectrum of the planet Venus with results that are of promise. In geology, besides survey operations, useful economic work has been done in connection with the output of wolfram. Three new meteorite falls-all chondrites-have been reported for 1916-17 from northern India. The most notable item of economic geodetic work for the year has been the taking of hourly readings of a tide-gauge at Basra, erected in connection with military requirements. The constants deduced from the reductions of these readings have been transmitted to the National Physical Laboratory at Teddington, to admit of the tracing of tidal curves for 1917-18. Important also has been the compilation of a list of the plumb-line deflection stations of India and Burma.

The work undertaken in connection with plant- and animal-pathology has been useful and varied. In this relationship an item which deserves attention is an account of

practical tests of the use of hydrocyanic acid gas for the destruction of vermin. While less successful than might be desired in the case of houses, this method has proved satisfactory as regards railway carriages and ships.

Appended to the report is a memorandum on work done for India at the Imperial Institute. A striking item in this memorandum is the record of a sample of Assam-grown flax, valued in London under war conditions in December, 1916, at £150 per ton, which was found to compare favorably with the medium qualities formerly received from Belgium.

Perhaps the time is approaching when a body, similar in its functions to this Indian board, may be brought into being so as to ensure for the scientific departments of our various Crown Colonies that correlation of effort which, as this report testifies, already so happily attends the operations of the different scientific departments of the Indian government.-Nature.

SCIENTIFIC BOOKS

Plant Genetics. By JOHN M. COULTER and MERLE C. COULTER. The University of Chicago Press. 1918. Pp. 214.

As the authors state the book is neither a technical presentation of genetics nor a general text, but is the outgrowth of a course of lectures designed to give general students of botany a brief introduction to the subject of genetics. This has been attempted in some 200 small pages with numerous diagrams. It is written for younger students than the books on genetics which have so far appeared. Necessarily a minimum of illustrative material has been used and the complex features are omitted altogether or are only briefly alluded

to.

An account of the earlier theories of heredity and a discussion of the inheritance of acquired characters opens the book followed by several chapters on Mendelism. The simplicity of the examples of the various types of Mendelism and the diagrams to illustrate them is a real achievement. Some misrepresentations of facts are to be noted here which are hardly

excusable even on the plea of pedagogical necessity. For example in the treatment of Mendel's pea hybrids the "wrinkled-smooth " seed character is given as similar in time of expression to the "tall-dwarf" plant character which in inheritance is one generation later in its apparent effect so that the statement that first generation dihybrid plants will all be tall and smooth-seeded individuals would be quite confusing to the beginning student if he repeated such an experiment for himself. For the purpose of illustrating the behavior of a dihybrid it serves the authors' purpose but there is certainly no lack of material which could be used equally well to illustrate this point without alteration of the actual facts.

The work of East, Shull, Emerson, Blakeslee and many others is freely drawn upon in bringing out the different phases of the subject. The chapters of chief interest to the geneticist are those on Parthenogenesis and Vegetative Apogamy, Inheritance in Gametophytes, and the Endosperm in Inheritance. A number of facts in regard to sex determination in plants have been gathered together. All these subjects have usually been scantily treated in books on genetics.

In the opinion of the writer the authors were not wise in including the complex subject of sterility in an elementary book of this kind especially as it is treated in the chapter on self-sterility. The beginning of the chapter emphasizes the importance of self-sterility as a means of insuring cross-pollination while the remainder is largely devoted to Belling's work on semi-sterility which has no significance in this connection. No clear distinction is made between the different types of sterility which would seem desirable if the subject is to be discussed at all. A chapter is devoted to the subject of hybrid vigor and the book closes with an able summary of the theoretical points involved in a consideration of the chromosomes as the bearers of the hereditary determiners.

Throughout there is shown a first-hand unfamiliarity with the genetical experiments discussed. In spite of this handicap a really

useful book, for those not primarily interested in genetics, has been produced which shows the authors' ability to coordinate many different, specialized fields of investigation and to put the results into an easily read form. The book is designed to fill an important place which would justify more care in the choice of material and in its presentation. The practise followed of giving few facts and discussing them in all their important relations to each other and to other fields of biology is perhaps the most valuable feature of the book. D. F. JONES CONNECTICUT AGRICULTURAL EXPERIMENT STA., NEW HAVEN, CONN.

THE POWER SITUATION IN THE
UNITED STATES

Two of the most important domestic problems facing the United States at the present time concern the supply of power necessary to maintain the industrial activities of the country, and the adequacy of transportation to move the raw materials and finished products involved in these activities. As the coal consumed in the United States engages over a third of the freight capacity of our railroads, and more and more coal is being used, the result is a growing burden upon transportation which must be relieved. The power problem and the transportation problem, therefore, are really different expressions of a single fundamental issue. In this connection the United States National Museum, Smithsonian Institution, has just issued a 50-page Bulletin, entitled "Power: Its Significance and Needs," which gives an analysis of the whole situation and presents a plan whereby the problems of water-power, coal-supply, and transportation may find a solution. This contribution is by Chester G. Gilbert and Joseph E. Pogue, of the Division of Mineral Technology, and is Part 5 of Bulletin No. 102, the Mineral Industries of the United States, which has already dealt constructively with such matters as coalproducts, fertilizers, domestic fuel and petroleum.

Quoting from the conclusions of the authors of this Bulletin, it is stated:

The righting of the power situation requires (1) the establishment of a comprehensive system of electric transmission lines to be administered as a common-carrier system like the railways. (2) The provision of such a system will necessitate the coordinated growth of central power stations in coal fields and at water-power sites, and in doing so will open to business enterprise a tremendous field of opportunity hitherto closed off from entry, and thus lead to the balanced development of the two major energy resources, coal and water-power. (3) The principle of multiple production, recognized and incorporated in national policy, will supplement the additional service gained through the organized employment of the electrical principle; applied to the production of coal-generated electricity, and, through the medium of municipal public utility plants, to the distributive employment of coal, this principle will effectively correlate the recovery of the commodity and energy values, so as ultimately to effect a full saving of the former and an increased gain of the latter, thus permitting a further relative diminution of the amount of fuel calling for transportation in bulky form. The first two points reduce themselves to a single issue, which is purely a business proposition to be handled by a business organization; the third item is more intangible and it is a matter of policy, which, therefore, can not be delegated or otherwise handled in objective fashion.

The provision of a common-carrier system of transmission lines, in brief, is the key to the whole problem. Its establishment will remove the retarding influence of high interest rates and antagonistic misunderstanding that has blocked waterpower development, and will afford the point of departure from precedent in favor of coal-field generation of electricity. Owing to the magnitude of the issue and the manifold lines of progress directly at stake, the development will provide a nuclear point for the establishment of a constructive economic policy, needed not merely for the full development of this field but as well for proper unfoldment of the industrial possibilities of the country in general. As such a policy has not developed in the past because of economic sectionalism growing chiefly out of an unequalized development of the energy resources, the nationalization of industrial opportunity attainable through a balanced development of power supply will clear the path of the main obstruction to unified action.

Thus specific action in respect to establishing a common-carrier system adapted to the power needs of the country will not only go far toward solving

the problem of transportation, but it will improve the fuel supply, correct the economic fallacy of drawing upon capital resources while neglectful of income, contribute to the recovery of the values now lost in the consumption of raw coal, lead to an adequate development of electrochemical activities, cut off a needless annual expenditure running well beyond the billion dollar mark, and constitute a potent contribution in the direction of stimulating the upgrowth of a constructive economic policy of national scope attuned to the needs of modern industrial development. It is believed that these results would involve national economies, offsetting in large part the cost of the war.

SPECIAL ARTICLES

THE COEFFICIENT OF EXPANSION OF LIVING TREE TRUNKS

THE present investigation was undertaken as a continuation of the work of the late Professor C. C. Trowbridge, of the Department of Physics, Columbia University, on the movements of the branches of trees, with the object of inquiring into the mechanism of these movements. Part of the work had been carried out in collaboration with Professor Trowbridge.

The measuring apparatus, as devised by him, consisted of a rod of invar, with four steel knobs set on short steel posts fitted into the rod near one end, at intervals of ninety degrees, and also with one or more small brass blocks in the form of square prisms, fitted over the rod at some distance from that end. A steelpointed block and a conical steel socket were attached to the tree under investigation, and a measurement was made by holding one of the steel balls in the socket, and making a light scratch on the brass plate by gently drawing it over the steel point. A careful record was kept of the exact position on the brass plate of each of the scratches made, and the distances between them were measured under the microscope. In the tests made previous to the treetrunk work, the instrument was found to be suitable for general laboratory work as well as

1 C. C. Trowbridge, "The Thermometric Move ments of Tree Branches at Freezing Temperatures," Bulletin of the Torrey Botanical Club, 43, No. 1, pp. 29-56, 1916.

for special types of investigation. Together with each measurement a reading was taken of the air temperature as given by a mercury thermometer attached to the tree, as well as the reading of one or more thermometers inserted into the tree to various depths.

Observations were made on a European linden tree (Tilia europæa), and a plane tree (Platanus orientalis), both on the campus of Columbia University. The observations extended from February 2 to May 19, 1917, and from December 22, 1917, to April 25, 1918. During the first winter, observations were made on both of these trees, but attention was confined to the linden tree alone during the second winter, as the same effects were observable here to a far more marked degree. During both winters, longitudinal and transverse measurements were made, a separate point and socket being used for each, and a longer rod being used for the longitudinal observations, as the longitudinal changes were, as a rule, much smaller in amount. An extended series of measurements was also made on the changes in the circumference of the tree and on frost cracks, during the second winter. Three interior thermometers were used in the first winter's observations, four in the second, one extending to a somewhat greater depth than the deepest of the previous winter. No observations were made during the summer, as it was found that at ordinary and high temperatures, the changes in dimensions were extremely slight. Observations were made from one to four times a day, and readings of the various thermometers were sometimes taken more frequently. During the winter of 1917-18, the writer made 109 sets of measurements, and about the same number during the preceding winter.

The second winter's observations fully confirmed the earlier series, and added some new results. In regard to the transverse measurements, it was found that above 32° Fahrenheit there is a slight expansion with rise in temperature, while below that temperature the changes are far more marked. As the temperature falls below 32° Fahrenheit there is a very marked transverse contraction. The dif

ference in the changes above and below freezing may best be illustrated by stating, in the case of the linden, that above the freezing temperature, the coefficient of expansion is nearly the same as that of dead wood, i. e., of the order of 5 X 10-5, while below freezing it is some fifty times as great.

The transverse change in dimensions of the tree, below freezing, usually lags behind the change in temperature of the bark by several hours at least, often as much as twenty-four hours. When there is a sudden change in the temperature of the bark, the contraction is rapid, but not synchronous. With a rise in temperature, the lag, as a rule, is relatively greater. It is probable that the temperature at a depth of four or five inches has little or no influence on the changes in transverse dimensions.

In the case of longitudinal measurements the fact was revealed that below the freezing temperature there is a minute but extremely definite increase in length with fall of temperature, and that above freezing, there is an equally minute increase with rise of temperature. At extremely low temperatures, near zero, Fahrenheit, however, there is a small contraction with fall of temperature, but when the temperature rises again, the expansion is extremely rapid, and by the time the temperature is again the same as before the drop, the tree is very much longer than previously.

In this series of measurements at very low temperatures, there is distinct evidence of two changes-thermal and physiological, apparently acting in opposite directions. At slightly higher temperatures the thermal change is not so much in evidence, and so, as a rule, only the physiological expansion with drop of temperature is observed. There is evidence of a lag of longitudinal expansion and contraction behind the temperature of the bark of the tree, but excepting at the lowest temperatures, the phenomenon is not clear cut, as in the case of the transverse measurements, and the details have not as yet been worked out.

A very extended series of measurements was made on the circumference of the linden tree,

and it was found that, as a rule, the expansions and contractions were in the same direction as for the transverse measurements, but yet this was not always the case. The changes in circumference were found not to be proportional to the transverse measurements. After more than four months, when the temperature was much higher than at the time observations were begun, the circumference of the tree was still smaller than when the first observations were made. The method of making observations on the circumference consisted in measuring, with a pair of dividers, the distance between two scratches on a painted steel tape surrounding the tree, and continuously left in contact with it. When the series of observations was begun, two scratches were made, one on each of the two parts of the tape which lay, one directly above the other, and, as the circumference changed, the distance between these scratches was recorded. These measurements were made several times a day, and showed that the final contraction, which Grossenbacher thought might possibly be due to an error in his measurements, is an actual experimental fact. Grossenbacher's observations were made at intervals of several weeks, and his tape was removed after each observation.

An equally extended series of measurements on frost cracks was made during the winter of 1917-18. It was found that during the coldest weather when the crack was open about three fourths of an inch, its depth at certain points was more than ten inches. Also, in addition to the large crack formed on the south side of the linden tree, another was formed on the north side toward the end of January, 1918, and the change in the width of the two cracks seemed to follow the same law, i. e., the cracks became wider as the temperature fell, and narrower as it rose again.

From the measurements on the transverse changes, on the circumference and on frost cracks, the conclusion was reached that frost

2J. G. Grossenbacher, "Crown-Rot of Fruit Trees, Field Studies," N. Y. Agricultural Experiment Station, Geneva, N. Y., Technical Bulletin, No. 23, September, 1912, pp. 35-37.

cracks are caused by a tearing apart of the tissue of the tree, due to a great contraction. Both the circumference and the transverse dimensions are much less when the crack is open than when it is closed, and the one is not proportional to the other. Frost cracks are probably due to a difference in the coefficients of radial and tangential contraction of the tree, a difference which sets in at approximately 25° Fahrenheit (about 4 degrees below zero Centigrade). If the cells of the tree collapse in a tangential direction (a fact which was observed) and the changes along the medullary rays are not as great, then the tree will split open, due to the increased tension. If the cells again expand tangentially, the crack will close due to increased pressure, provided the radius may not change in dimensions at all, it may expand to a greater extent, or it may even contract; in any case the crack will close. The first or third of these cases would account for the observation that after the crack has closed, the circumference of the tree is less than before it opened. These conclusions are, however, tentative and approximate, due to the complications caused by the lag in the tangential direction, the temperature gradient through the tree, and other difficulties which must still be studied, before a more complete explanation can be given.

C. C. TROWBRIDGE, MABEL WEIL

PHENIX PHYSICAL LABORATORIES. COLUMBIA UNIVERSITY

THE DEPTH OF DOLOMITIZATION1

IN a recent issue of the American Journal of Science, there appeared an article by E. W. Skeats on 66 The Formation of Dolomite and its Bearing on the Coral Reef Problem." The author of this paper adopts the replacement theory of the origin of dolomite and presents

3 Some similar conclusions were reached by a different method by Caspany, Bot. Zeit., 15, 1857. 4 Deceased.

1 Published with the permission of the Director of the Iowa Geological Survey.

2 Volume XLV., 4th Series, pp. 185-200, March, 1918.