EXPERIMENT STATION EECORD. 625 



AGRICULTURAL BOTANY. 



Handbook of technique for teachers and students of natural science, B. 

 SciiMiu {Iluiidbiivli ilcr iialunjcscltii-lttliclicn Tcvhiiih: y>r/p.s-(c; B. (J. Trubiicr, 

 191.'h PP- VIII-\-555, figs. 381). — This book, prepared by collaboration of the 

 15 authors named, is intended to bring together such information, directions, 

 and suggestions as may prove helpful to instructors or students in any one of 

 several branches of natural science. It is divided into sections partly corre- 

 sponding to the usual divisions and the main requirements of such work in 

 the field, laboratory, and museum, but partly groupiug together features of more 

 general ai)plicMtiou and common technique, as in photography. 



The arrangement, ]u-eparation, care, and use of the hiboratory, specimens, 

 materials, and instruments, covering a wide range of studies, are treated in 

 more or less detail. Lists are given of related scientific and pedagogic litera- 

 ture, and the work concludes with an index. 



Culture media for use in the plate method of counting soil bacteria, 11. 

 J. Conn (Xew York titntc Sta. Tcvh. Bui. 3S (191',), pp. 5//).— The author 

 describes the use of two culture media, one of which is a soil-extract gelatin 

 and the other an agar medium containing no organic matter except the agar, 

 dextrose, and sodium asparagluate. 



The soil-extract gelatin is recommended for use when the plate method is 

 employed as a preliminary procedure in a qualitative study of soil bacteria. 

 The chief advantage of the asparaginate agar is said to be that it contains 

 no substance of indefinite composition except the agar itself. This, it is 

 thought, would allow compai'able results to be obtained by its use, even 

 though the work was done in different laboratories by different individuals. 



Four other media that have been recently discussed were compared with 

 the media mentioned above, but for qualitative work they were all found to 

 be inferior. For quantitative work they are said to be undesirable because 

 they contain substances of indefinite composition. 



The chemical dynamics of living protoplasm, W. J. V. Ostekhout {Ahs. in 

 Science, n. ser., 41 {1915), No. 101,8, p. 17Ji). — The author claims it is possible, 

 by means of electrical measurements, to follow reactions in living jirotoplasm 

 without interference with the progress of the reaction or injury to the proto- 

 plasm. It is also considered possible to determine the order of the reaction 

 and to ascertain whether the reaction is reversible. In many cases it appears 

 that the reaction is reversible up to a certain point, but beyond this it is 

 irreversible. 



The mechanism of exchange between plants and external media, P. Maze 

 {Coinpl. Rend. Acad. Sci. [Paris], 159 (1914), No. S. pp. 27i-27.J).— Claiming to 

 have shown previously (E. S. II., 31, p. 221) that the elaboration of a given 

 weight of vegetable matter requires the use of a constant volume of nutritive 

 solution of definite composition and concentration (this law dominating the 

 whole economy of the plant and regulating excbanges with its external me- 

 dium), also that roots excrete mineral and organic substances, this fact disa- 

 greeing with the hypothesis of a pi-otoplasmic semipei'meable membrane, the 

 author gives tabulated results of a study on the role of osmosis in this connec- 

 tion as exemplified by maize growing in sun or shade and supplied with a ' 

 nutritive medium including from 2 to 5 per cent of sugar. 



The conclusion is drawn that the law of osmosis does not operate in any 

 important degree to affect exchanges occurring between roots and nutritive 

 solutions. The plant, it is held, constitutes a system permeable to water . 

 and to substances in solution or in colloidal suspension therein, but its per- 



