866 



SCIENCE 



[N. S. Vol. XXXI. No. 805 



part the reviewer leaves to a more capable 

 pen. Professor B. E. Livingston contributes 

 a section on the soils of this domain. He de- 

 scribes these soils in some detail, and there 

 follow data derived from a detailed study of 

 the soil moisture content at given depths for 

 a period extended between October 3, 1907, 

 and April 11, 1908. The importance of such 

 information is shown in the fact that the ef- 

 fect of precipitation lags behind the precipi- 

 tation itself, which " consideration empha- 

 sizes the inadequacy of mere precipitation data 

 in any attempt to determine the moisture con- 

 ditions under which the plants of any region 

 live." Elsewhere, Professor Livingston points 

 out that the " distribution of plant forms is 

 perhaps more often determined by availability 

 of oxygen than that of water," and this is of 

 importance for desert plants, many of which 

 appear to suffer from lack of oxygen in soils 

 too abundantly supplied with moisture. Pro- 

 fessor Spalding concludes that the facts es- 

 tablished by Livingston show a remarkable 

 degree of correspondence with the facts of 

 distribution. 



Professor J. J. Thornber, in a few pages, 

 gives an exceedingly important summary of 

 the vegetation groups of the domain. The un- 

 importance of biennials is remarked, only 

 three species being noted, in contrast to a 

 total of 230 annuals. Of these, the winter an- 

 nuals are three times more numerous than 

 those of the summer. The total number of 

 perennials is about equal to that of the an- 

 nuals. Numerically the grasses (70 sp.) and 

 the compositae (65 sp.) are dominant. 



Of the lichens, of which at any rate 24 

 species are reported, enough, based on the 

 study of them by Professor Bruce Pink, is 

 said to indicate that a fruitful field of study 

 awaits one who is disposed to attack these or- 

 ganisms in their desert habitat from an eco- 

 logical point of view. 



Dr. D. T. MacDougal deals trenchantly 

 with the live question of the origin of desert 

 plants. He sees little evidence that individual 

 capacity in the soma has resulted in adapta- 

 tion to desert conditions. The mesophytic 

 forms which have extended to the desert 



regions flourish only during the mesophytic 

 periods. Observed responses to true desert 

 conditions are not necessarily adaptive, nor is 

 it possible to refer highly specialized char- 

 acters to the " supposedly causal conditions 

 which they meet," such as the spines and 

 glochidia of cacti. This is well said. 



The weight of experimental evidence, de- 

 rived from the work of Tower, Gager and 

 MacDougal, the latter especially, indicates 

 that the effects of environmental changes in 

 the germ plasm are accountable for " irrevers- 

 ible changes in a hereditary line by which new 

 combinations of qualities and new characters " 

 become " fully transmissible." Dr. Mac- 

 Dougal properly points out the mental bias 

 which has led to the regarding of desert 

 plants as highly specialized, and mesophytes 

 as not. What would the trained botanist of 

 desert antecedents have thought on viewing, 

 for the first time, a mesophytic forest! 



It is clear from this cursory glance at the 

 volume under review, embracing only a few 

 of its more striking features, that a great deal 

 of careful, insistent inquiry has been carried 

 on by all the authors. This, it is equally evi- 

 dent, is leading us steadily in the direction 

 of illuminating generalizations, which ex- 

 press more rational notions about plants than 

 those which have bpld the botanical mind in 

 thrall for many years. We are getting, as an 

 example, a proper notion of adaptation, by 

 which the word itself is condemned. This 

 notion is not new, but is widely unaccepted in 

 practise as yet, and this is well enough if it 

 forces us to bring about an adequate investi- 

 gation of the facts. 



Much remains to do, or, better, shall we say 

 truth if we admit that even the beginnings 

 yet made are small. But beginnings in the 

 right direction are notable, and Professor 

 Spalding's work is such. The reviewer avows 

 his warm admiration and regard for him who, 

 after many years of rare service as a teacher, 

 has devoted much of his remaining strength 

 to a trying field of research, fruitful of basic 

 truth in method and result. 



Prancis Ernest Lloyd 

 Alabama Polytechnic Institute 



