200 BOTANICAL GAZETTE [march 



conditions respiration was found to be irregular. Photosynthesis was depressed, 

 probably by the direct action of the gas on the chlorophyll, and not by a closing 

 of the stomata (Betula alba and Salix); while transpiration is not depressed by 

 the gas in any concentration. The rate of absorption of water is not reduced, the 

 removal of the products of photosynthesis is delayed, and growth is retarded. 

 In spite of all these effects of the gas, the author regards them as insufficient to 

 account for the chronic injury. In a later chapter he reasons that the cause of 

 the chronic injury must be sought in the effect of the gas on the soil, in which a 

 condition similar to that present in cedar bogs is brought about. All the effects on 

 trees point to a death by drouth. 



Other chapters deal with the relation of soil conditions to the growth of trees, 

 and with the resistance of various plants to smoke injury. Finally, the methods 



smo 



As a whole, the work is a record of careful experiments and observations on 

 this ver>' obscure subject. The great difficulty of properly diagnosing injurious 

 effects due to smoke is repeatedly emphasized. Even in the carefully guarded 

 ex-periments, the individual differences of different plants, as well as unfavorable 

 factors due to the conditions of the experiments, often tend to obscure the effects 

 of the dilute mixtures of the gases used. All this, however, has served to draw 

 the author's attention to an important phase of the subject which has hitherto 

 probably not been sufficiently considered, that is, the effect of the acids of smoke 

 m the soil. Through chansres induced bv the continuous accumulation of SO2 



bottom 



about 



.VSSELBRING 



MINOR NOTICES 





ual of micrography.— Dr. J. W. Moll, professor of botany in the RoyaJ 

 University of Groningen, has prepared a manual^ for the use of beginners in 

 laboratory practice in botany, which he believes is adapted not only to enable 

 them to gain useful information by their own efforts, but also to train them in 

 proper methods of scientitic work. The book is the outgrowth of the author's 

 experience, which has led him strongly to deprecate the use in the laboratory of 

 books which teU the student what is to be seen. In the preface he sets forth his 

 views vigorously on the pedagogics of botany, with special reference to the place 

 of practical exercises. 



The book is divided into three parts. The first gives a brief account of 

 instruments, reagents, and materials; and the second gives directions for the 

 analysis of microscopic structure and outlines for micrographic descriptions. 

 The thhti part contains 489 exercises, which are scarcely more than lists of the 

 n ^erial and preparations needed. Of course such exercises presuppose verbal 



3 MoLt, J. W., Handboek der botanische micrographie, ten gebruike bij de prac- 

 tiscbe oefeningen voor aanstaande medici, pharmaceuten en biologen. Small Svo- 

 pp. VI .u 356. fig,_^ Groningen : J. B. Welters. 1907. #.4.25. 



