6o IVyomiiig Experiment Station. 



lish the vertical zones on account of the comparatively 

 limited observations yet made within the wide borders of 

 a great state. Rather something may be said of certain 

 "areas or characteristic regions. 



THE PLAINS FLORA. 



The regions referred to as plains differ greatly in 

 respect to soil, rainfall and altitude. All are compara- 

 tively level tracts of land devoid of arboreal vegetation, 

 if one excepts the occasional border of Cottonwoods on 

 stream banks. In this report no mention can be made of 

 the plains of the north-eastern, nor of the south-western 

 parts of the state, for these regions are yet to be visited. 

 It is, however, well known that both these regions differ 

 materially from the rest of the state and from each other. 

 The former, with a considerable rainfall and "gumbo" 

 soil; the latter, sandy soil and a minimum of rain. Care- 

 ful exploration in these two regions will add a large num- 

 ber of species to the list of the state. 



The plains from which we have reports, meagre as 

 yet, are the Laramie Plains; the plains lying east of the 

 Laramie Mountains, and south of Lusk; those bordering 

 on the Platte River, and those northward from the Platte 

 through the center of the stat« to Lander; the plains ad- 

 jacent to Wind River, and those of the upper part of the 

 Green River valley; also the Gros Ventre valley, and Jack- 

 son's Hole. Through this latter mountain-enclosed, pla- 

 teau-like plain flows Snake River. 



All of these may again be classified, either as a whole 

 or in part as: I. Sandy, or gravelly plains. 2. Alkali 

 plains. 



To the first class belong those whose soil is compara- 

 tively free from alkali and whose characteristic shrub, 



