3 5 2 BOTANICAL GAZETTE [april 



with this group, all plants with roots confined to the upper 2 feet of the soil 

 are grasses, and include such species as Koeleria cristata, Stipa spartea, Elymiis 

 canadensis , and Distichlis spicata. 



Such root systems are to be related to the deep, mellow, loess soil with high 

 water-holding capacity and moist subsoil. Here the data of Weaver cor- 

 - respond well with those of Alway 3 for moisture conditions, although the 

 former finds a much deeper root development than that assumed by the 

 latter. In the upper 4 or 5 feet there is usually at midsummer a reduction of 

 the water supply to a point below the wilting coefficient, these data cor- 

 responding with those of the reviewer for the grasslands of the Chicago region. 4 



The climatic conditions of the prairies of southeastern Washington are 

 shown to be more severe than those of Nebraska, not only because of a smaller 

 annual precipitation, but also because only one-third of this rainfall comes 

 during the growing season. As a part of the response, the early flowering 

 grasses predominate, and many of these, such as Koeleria cristata, Poa Sand- 

 bergi, and Festuca ovina have their roots confined to the upper 18 inches of 

 soil. There remain, however, some grasses and many dicotyledons that are 

 decidedly deep rooted. 



Some data also are given for a " chaparral" community transitional from 

 the prairie to the forest, and dominated by species of Symphoricarpos, Rhus, 

 Corylus, and Rosa. The designation is unfortunate, for the best usage would 

 limit the term "chaparral" to an evergreen scrub like that occurring on the 

 Pacific Coast of California. 



In comparison with the root systems of the prairies, those of the plains are 

 characterized by a larger percentage of moderately deep rooted species, fewer 

 very deeply rooted plants, and by a more extensive system of surface absorb- 

 ing and wide spreading laterals. Shantz* reported that at Akron, Colorado, 

 almost the entire root system of all the grasses is limited to the 18 surface 

 inches. The conditions are evidently different near Colorado Springs, for 

 there Weaver reports one grass only, Koeleria cristata, with roots confined 

 to the surface 2 feet. Grouping into layers is again evident; the most dis- 

 tinctive feature of the plains species, in addition to spreading laterals, is the 

 moderate penetration of the deep rooted species. This is doubtless due, as 

 indicated by both Weaver and Alway (loc. cit.), to the comparative impene- 

 trability of the extremely dry subsoil. 



The sand hill community exhibits in a still more striking manner the 

 development of a profusion of widely spreading laterals in the upper 2 or 



a Alway, F. J., et al., Relation of minimum moisture content of subsoil of 

 prairies to hygroscopic coefficient. Box. Gaz. 67:185-207. 1919. 

 *Box. Gaz. 58:193-234. 1914. 



* SHANTZ, H. L., Natural vegetation as an indicator of the capabilities of land for 

 crop production in the great plains area. U.S. Dept. Agric, Bur. PI. Ind. Bull. 201. 

 pp. 100. pis. 6. figs. 23. 191 1. 



