Aug. 7, 1916 



Vegetative Succession Under Irrigation 



747 



flooding system. With moderate moisture millet becomes even prolific 

 and attains a height of about 60 cm. 



Stipa comata is a good pasture grass, but the long awns may be fatal to 

 stock because of the presence of tiny barbs. On the range the animals 

 seek it either before the awns have developed or after they have fallen. 

 Altogether, it is fortunate that it is able to survive only one season of 

 meadow conditions. 



The next plant that needs more than mention is vetch, the only one 

 persisting of the 10 upland kinds listed. Its ability to persist makes it the 

 connecting link between the upland vetches and those of the lowland 

 which are to invade the developing meadow. 



The lupins (PI. C, fig. 2; CII, fig. 1), which persist a summer under 

 controlled flooding, could probably be perpetuated indefinitely under con- 

 trolled irrigation. However, since some species are strongly suspected 

 of being poisonous to stock, at least during certain periods of their growth, 

 their cultivation can not be advised, unless careful means are taken to 

 ascertain this fact as regards the local species. These are numerous, and 

 some are known to be not only harmless but of great value. Such is the 

 case with an Idaho species which I have seen form, with the farmer's 

 encouragement, a nearly pure stand on rather sandy bottom lands. This 

 was cut just before the pods became dry, and when fed mixed with hay, 

 both cattle and horses relished and thrived on it during the winter. 



The next list represents the chief contribution of the upland flora to 

 the growing meadow formation. 



UPLAND PLANTS TENDING TO DOMINANCE THE FIRST SEASON IRRIGATED 



Agropyron albicans R. and S. 

 Agropyron dasystachyum (Hook) Scribn. 

 Agropyron mo lie Rydb. 

 Bouteloua oligostachya (Nutt.) Torr. 

 Koeleria cristata (L.) Pers. 



Carex siccata Dewey. 

 Carex stenophylla Wahl. 

 Arabis hirsuta Scop. 

 Antennaria parvifolia Nutt. 

 Grindelia subalpina Greene. 



Nearly a dozen upland plants not only persist under controlled flood- 

 ing but even flourish, at least when they happen to be established on a 

 relatively high spot. With the advent of the first meadow plants (some 

 of which are next listed) two opposing elements must be considered, one 

 of which has had to adapt itself to an environment partially new. 



MEADOW PLANTS APPEARING ON UPLAND THE FIRST SEASON IRRIGATED 



Hordcum jubatum L. 

 Sporobolus brevifolius (Nutt.) Scribn. 

 Juncus longistylis Torr. 

 Astragalus Bodinii Sheld. 



Astragalus hypoglottis L. 

 Oxytropis dejlexus DC. 

 Plantago eriopoda Torr. 



By the end of the first summer these typically meadow plants are 

 almost certain to be represented, sometimes only by scattered individ- 



