67 



control of the distribution of these plants. Other regulative 

 factors, such as temperature, rainfall, humidity, etc., all carefully 

 measured, come in for their share of attention. 



Still under the general heading of local distribution are sections 

 devoted to dispersal, invasion, competition, and succession, in 

 which the author attempts to trace some of the other factors 

 bearing on the distribution of the plants in the area studied. A 

 section on the root system of Cereus giganteiis is here introduced 

 by Dr. W. A. Cannon. 



Space forbids an account of the chapter on environmental and 

 historical factors. There are included within it sections on the 

 geology and soils of the region written by C. F. Tolman and 

 B. E. Livingston respectively. 



Chapter four is taken up with the vegetation groups of the 

 desert laboratory domain and is contributed by Professor J. J. 

 Thornber. It contains lists of the plants growing on the various 

 major formations found in the area, and also considerable sta- 

 tistical matter. 



The chapter on the origin of desert floras is contributed by 

 Dr. D. T. MacDougal. This brings into co-relation much of 

 what has been treated specifically in earlier parts of the work. 

 Some of this section has already seen the light in the Plant World 

 for September, 1908. 



Dr. Spalding has collected and put on permanent record a 

 mass of very interesting and essential facts dealing with the sub- 

 ject in hand. Throughout there is a creditable hesitancy in 

 drawing conclusions, some of which might have been warranted 

 in view of the wealth of detail. The statistical and graphic part 

 of the work is splendid ; and work like this and that done by 

 Jennings and others will undoubtedly serve as the bases of 

 numerous ecologic palimpsests. 



The illustrations and typography are all that could be desired. 



Norman Taylor 



