September i8, 1919] 



NATURE 



47 



book which will give the student a knowledge of 

 the botany of common orchard, garden, and field 

 crops. ..." A text-book which achieved this 

 object would be indeed a boon, for, with the 

 exception of Percival's "Agricultural Botany," 

 we know of no book which treats of economic 

 plants in such a way as to expound the principles 

 of botanical science and to provide knowledge 

 directly useful to the person interested in the 

 cultivation of food crops. 



The method adopted by the author is to give 

 a rapid exposition of botanical principles — histo- 

 logical, physiological, genetical, and morpho- 

 logical — in the course of sixty-seven pages, and 

 then to treat in some detail the series of crop 

 plants of field, gardeh,' and orchard. 



This method is open to the fatal objection that 

 it evades the first duty of the teacher, which is 

 so to select and present common facts that the 

 essential generalisations, which cohere them into 

 a scientific system, either suggest themselves to 

 the student's mind, or, at all events, appear 

 natural and convincing when the teacher, as is 

 often the case, is compelled by the defectiveness 

 of his method, or the indifference of his students, 

 to expound them. 



Instead of attempting this the author is content 

 to hand out the usual stock of botanical facts. 

 He begins by talking about undifferentiated plants 

 and a thallus (p. i), tells the student in p. 2 that 

 the tendril of a pea is morphologically a leaf, and 

 a potato tuber a modified stem, when, of course, 

 the duty of the teacher is to promote the discovery 

 by the student of these facts, and thereby to 

 stimulate interest, illustrate morphological prin- 

 ciples, and train the eye and mind to see essential 

 things. 



Histology is dealt with in chap. ii. in six pages, 

 and the student is told sundry facts — that leuco- 

 plasts and chloroplasts exist, that protoplasm is 

 a "proteid "and that it feels slimy, that the cell- 

 wall may contain lignin, suberin, cutin, and 

 pectin. Even in the general introduction it is 

 evident that the mind of the writer is set on the 

 "practical " economic part which is to come later. 

 Thus (p. 25) he asserts as a general truth that 

 many new varieties of fruit are bud varieties, that 

 a certain branch on a tree is seen to possess pecu- 

 liarities, and that it is taken off and propagated 

 as a new variety. A more misleading statement, 

 if intended to be of general application, it would 

 be hard indeed to make. It would be interesting 

 to know what variety of apple, pear, plum, 

 currant, raspberry, or gooseberry is known to 

 have arisen by bud variation ! 



Part ii., which consists of nearly 600 pages, 

 / contains much useful information with respect to 

 *■; the botany of cultivated plants. Members of the 



> Graminese — cereal and other — are treated of at 

 \ length and well, though from the teacher's point 



> of view the work is too full for a text-book, and 

 % not full enough for a work of reference — for 



example, Mendelism is dealt with in half a page 

 (p. 421), and, needless to say, the few words 

 devoted to this all-important subject are not ade- 

 NO. 2603, VOL. 104] 



quate to impress the student with the value of 

 this method of genetical research. 



The book contains much miscellaneous informa- 

 tion which may perhaps interest the American 

 student — that 44 million pounds of dried apples 

 were produced in the United States in 1909, and 

 that in 191 5 more than 230 million bushels of 

 apples were produced in that country; but, so far 

 as may be discovered, nothing ' is said on the 

 fascinating subject of pruning, which might, if 

 scientifically treated, be the means of illustrating 

 many important principles of physiology. Excel- 

 lent as is much of the matter which it contains, 

 this volume does not, in our opinion, give agri- 

 cultural and horticultural teachers or students 

 what they want — a new presentation of botanical 

 principles based on the study of those plants 

 among which they have to work. F. K. 



OUR BOOKSHELF. 

 Practical Pyrometry : The Theory, Calibration, 

 and Use of Instruments for the Measurement 

 of High Temperatures. By E. S. Ferry, G. A. 

 Shook, and J. R. Collins. Pp. vii-t-i47. (New 

 York : John Wiley and Sons, Inc. ; London : 

 Chapman and Hall, Ltd., 1917.) Price 7s. net. 

 The subject of pyrometry, so important nowadays 

 in many industrial processes, is not as yet over- 

 burdened with literature of the text-book descrip- 

 tion. The present volume contains in a small 

 compass most of the information required for an 

 intelligent understanding of the principles and in- 

 structions as to the correct methods of manipula- 

 tion of pyrometers, including the mathematical 

 theory. Descriptions of historical interest only, 

 with which such books are often burdened, are 

 omitted, and the subject-matter is well chosen to 

 give helpful instruction. 



A separate chapter is devoted to each of the 

 four principal types of pyrometer — namely, the 

 resistance, thermo-electric, radiation, and optical 

 pyrometers — with a preliminary chapter on the 

 standard temperature scales. The best chapter 

 in the book is that on optical pyrometry ; the 

 principles and construction of the various varie- 

 ties are very clearly described and in a more 

 thorough manner than is usual in text-books. 



Exception might be taken to the omission of 

 some of the simpler forms of pyrometer, such as 

 the water pyrometer and the mercurial expansion 

 and sentinel types. These appeal to many manu- 

 facturers, especially where great accuracy is not 

 required, and guidance as to their use would 

 therefore be acceptable. 



The book is written for three classes of readers 

 — college students, technically trained men who 

 deal with processes requiring high-temperature 

 measurements, and less trained observers who 

 may make the measurements. To this end the 

 more mathematical portions, such as Foote's 

 mathematical investigation of cold junction error, 

 and the more mathematical treatment of optical 

 pyrometers, might with advantage have formed 

 separate appendices for particular study, rendering 

 the text clearer for the less technical reader. 



