y44 Journal of Agricultural Research vol. vi.no. 19 



determined purely by the bounds of the unit, as indicated above. Since 

 these bounds are of more or less arbitrary definition in themselves, the 

 disposition of plants within them is of like nature, though it may be said 

 that, in general, the fullest development of a given species normally 

 occurs within the unit in which it is placed. 



Any one of the four wheat-grasses may be dominant or principal spe- 

 cies — that is, it may make up the bulk of the vegetation over large areas 

 of this unit (PI. CII, fig. 2). The kind with which we are most concerned, 

 however, reaches its best development in another complex. 



Indian millet (Oryzopsis hymenoides) , though of great importance from 

 a nutritive standpoint, 1 is largely confined to loose, somewhat sandy 

 soils; and therefore its possibilities for forage development are limited to 

 regions of that nature. 



Attention is called to the large number of legumes in this complex — five 

 kinds. These will be augmented by five more, distributed among the 

 remaining complexes. Legumes require rich soils of high lime content, 

 the significance of which will develop later. 



The remaining plants are nearly all xerophytes, species eminently fitted 

 in one way or another to withstand the rigors of the environment in which 

 they live. It is not surprising that such plants will take no part in an 

 artificial transformation of this bench to meadow, where new conditions 

 are suddenly introduced which are directly opposed to those to which 

 these species have become so well adapted. Their disappearance in many 

 cases means the loss of the most nutritious plants on the range. 



CHARACTERISTIC DRAW, OR GULLY, PLANTS 



Astragalus spp. (two species). 

 Lupinus parjiflorus Nutt. 

 Antennaria parvifolia Nutt. 

 Artemisia cana Pursh. 

 Grindelia subalpina Greene. 



Bouieloua oligosiachya (Nutt.) Torr. 

 Koeleria cristata (L.) Pers. 

 Stipa comata Trin. and Rupr. 

 Carex spp. (two species). 

 Zygadenus intermedins Rydb. 

 Delphinium Geyeri Greene. 



The bench lands are interrupted at irregular intervals by swales, or 

 draws. These carry away the surplus surface water to the stream, so 

 that those that drain a considerable area become gulches. Plate C, 

 figure 2, gives a good average idea of this topographical feature. The 

 chief difference, as compared to the bench proper, is the more constant 

 water supply, which is somewhat greater and which lasts longer. It is 

 not surprising, therefore, that over 69 per cent of its more characteristic 

 plants (as given above) will persist (in some cases attain greater develop- 

 ment) during the first season under irrigation. 



Among those that will not be able to stand the new conditions are 

 Delphinium Geyeri and Zygadenus intermedins, both a constant menace to 



1 Knight, H. G., Hepner, F. E-, and Nelson, Aven. Wyoming forage plants and their chemical com- 

 position— Studies no. 3- Wyo. Agr. Exp. Sta. Bui. 76, 119 p., 50 fig. 1908. 



