CURRENT LILERATURS 
BOOK REVIEWS 
Root systems 
root systems of grassland plants, and the present publication is confined to 
grassland vegetation and to the crop plants grown within its limits. The 
grasslands are considered under the three subdivisions of true prairie, mixed 
prairie, and short-grass plains. 
e true prairie is characterized by tall sod-forming grasses growing in 
soil of rather abundant water content, with greater moisture in the subsoil. 
On the basis of root development, three general classes may be recognized in 
grassland vegetation. In the first the “working depth,” or average depth 
reached by a large number of roots, is about 1.5 feet, with a maximum depth 
of 3.3 feet. The second class possesses roots with a working depth of 3.3 feet 
and a maximum of about 6 feet; while in the third class the working depth of 
the roots is usually 5-8 feet and the maximum penetration 8-12 feet, with 
a few species reaching an extreme of 15-20 feet. Examples of the three classes 
are Aristida oligantha, Elymus canadensis, and Koeleria cristata; Andropogon 
scoparius, Bouteloua gracilis, and Grindelia squarrosa; and Andropogon furcatus 
Aster multiflorus, and Panicum virgatum. The deeper rooted species have few 
roots in the surface layers of the soil, showing a grouping of roots into more or 
less definite layers, thus reducing competition and permitting the growth of 
a larger number of species. In the short grass plains practically all plants 
have root systems well adapted for water absorption from surface soils. 
Two have roots with a working depth less than 2 feet, three have working depths 
of 2-4 feet, and three have a range of 4-7 feet. Examples of the three classes 
are Opuntia polyacantha, Bulbilis dactyloides, and Psoralea tenuifolia. Here 
the water supply is much more limited, especially in the subsoil. The soil and 
moisture conditions, as well as the vegetation in the mixed prairie, are intes: 
mediate between the true prairie and the short-grass plains. Compared with 
the true prairie, the plants are not as deeply rooted, but have usually developed 
a very efficient and widely spreading absorbing system in the surface soil. 
The root systems of cereal crops grown at many stations in true and mixed 
prairie and short-grass plains were also examined. The comparative amount 
‘WEAVER, JoHN E., Root development in the grassland formation. Carn. 
Inst. Wash. Publ. 292. pp. 151. pls. 23. figs. 37. 1920. 
2 Bot. GAz. 69:351-353- 1920. 
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