10 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



serve to interpret these environmental conditions. Both of these 

 criteria are needed to reveal the judgment of plants as to the fitness of 

 the habitat in which they grow or in which crop plants are to be grown. 

 In classifying lands for afforestation, for grazing, or for agriculture, a 

 knowledge of root habit and extent is of prime importance. Indeed, 

 such a study not only forms a basis for judging the natural vegetation 

 as an indicator of the value of lands for crop production, but also for 

 determining the kind of crop to be most profitably grown (Shantz, 

 191 1). It readily leads to the intelligent solution of problems of range 

 improvement (Sampson, 1914, 1917, 1919), the selection of sites for 

 afforestation (Korstian, 1917), and of numerous other problems where 

 natural vegetation or crop plants are concerned (Clements, 1920). 

 The applications of a knowledge of the root development of crop plants 

 in the preparation of the seed-bed, rate of seeding, methods of tillage, 

 use of fertilizers, irrigation, and crop rotation are too patent to need 

 further discussion here. 



The method used in excavating root s}^stems, whether of native 

 species or of crop plants, was the same as that formerly employed 

 (Ecological Relations of Roots, 1919). By the side of the plant to be 

 examined, a trench was dug to a depth of about 5 feet and of conven- 

 ient width. This afforded an open face into which one might dig with 

 a hand-pick furnished also with a cutting-edge, and thus make an ex- 

 amination of the root system. This apparently simple process, how- 

 ever, requires much practice, not a little patience, and wide experience 

 with soil texture. In these investigations more than 1 ,500 root systems 

 have been examined, and for practically all of the species encountered it 

 has been possible to excavate the root systems almost in their entirety. 

 In cases where considerable reconstruction was necessary, this has been 

 rendered more accurate and less difficult by methods of record in the 

 field. The extensive examination of species at different periods and in 

 different soil types has permitted the choice of specimens for complete 

 excavation from soils when optimum water-content and working con- 

 ditions prevailed. With certain crop plants, and not infrequently with 

 native vegetation, the original trenches were deepened as work pro- 

 gressed and the working level often reached a depth of 8 to 10 feet, 

 sometimes much deeper. To assure certainty as to the maximum 

 depth of the root termini, the soil underlying the deepest roots was 

 usually undercut for about a foot below the root-ends and was carefully 

 examined as it was removed. 



The loot descriptions, except as otherwise indicated, are of mature 

 perennial plants. The former practice of examining several roots of 

 a given species and then writing a working description was followed. 

 This was kept at hand and as new roots of the same species were studied 

 any variation from the original description was noted. While many 

 of the root systems, especially those of the grasses, were removed in 



