BOOKS AND CURRENT LITERATURE '.y\'A 



of trees, shrubs, grasses and other herbaceous plants were determined 

 Rainfall, soil moisture, evaporation, and wind were measured in each 

 of the communities. It was found in several cases that the type of root 

 system in a given species is determined by the character of the environ- 

 mental conditions and the nature of the soil, although there are other 

 cases in which the type is specific and relatively constant. A great 

 deal of light has been thrown by Weaver's work on the layering of root 

 systems and the "competition" between roots of different plants in 

 the same soil level. 



In the prairies of eastern Nebraska more than half the species exam- 

 ined penetrate beyond 5 feet (including Panicum virgatum, Andropogon 

 furcatus, A. sooparius, and A. nutans) and many to 7 and 9 feet. Al- 

 though there are 20 inches of rain in the growing season in this region 

 it was found that there are times in that season when there is no avail- 

 able soil moisture down to a depth of 5 feet. It is in this soil that layer- 

 ing was found most common. In the prairies of southeastern Wash- 

 ington more superficial root systems prevail, in correlation with a lower 

 rainfall and earlier seasonal development. In the so-called chappiral 

 of southeastern Nebraska some very deep-seated roots were found,— 

 Rosa arkansana reaching 21 feet. On the plains near Colorado Springs 

 the roots of many characteristic species, including the grasses, are 

 found chiefly between 2 and 5 feet, although more than half of the 28 

 forms examined penetrate beyond 5 feet and down to 10 to 13 feet. 

 The lateral spread of the roots is greater here than in the prairies. In 

 the Rocky Mountains, near Colorado Springs, work was carried on in 

 the open vegetation of the gravel slides, the more nearly closed half 

 gravel slides, and the forest. The first of these habitats is character- 

 ized by shallow soil and superficial root systems, with no competition; 

 the second by both shallow and deep systems down to 4 feet, with all 

 the soil exploited by roots at 3 feet. In the forest the roots of trees, 

 shrubs, and herbs are found mainly in the first 18 inches. Determina- 

 tions from June to August showed a decrease of soil moisture with in- 

 creasing depth, down to 3 feet. 



Many characteristic root systems are illustrated, and a series of 

 colored plates is used to map the distribution of the roots of associated 

 species, as seen in a vertical section of the soil. The publication as a 

 whole forms a very substantial contribution to an important and 

 neglected field of work. — Forrest Shreve. 



