43 



the shnde of oak brush, the former also In abandoned fields. A. 

 Blmplicifoiius is rare on bare mesas at the north. A. Geyevi and 

 lentiginosiis are scattered over the sandy plains. A. subeiufroia 

 replaces pictus at the south. A. megacarpus is rare along th<^ ti^oh 

 draws and in the edge of the oak zone in very barren clay. A. urn- 

 phiovys is frequent over the sandy plains, as is A. pygmseus at the 

 north. A. cymboides and Musiniensis frequent the gravelly mesas. 

 A. Utahensis and Purshii are rare higher up, in the gravel. A. 

 sropulorum occurs in the oak brush. A. debilis grows in high uiea- 

 dops as does A. argophyllus. A. lonchocarpus grows on alkaline and 

 sandy flats and slopes. The uniis'"il spruce zone species occur on 

 the high Tiepk" b'lt tbey are not distinctive. The effect of barriers 

 Is such that the whole flora is very j-eculiar. Very few species ex- 

 tend -ivp" to tho Rio Grande drainage beyond the San Juan. A. as- 

 clepiadoides. Coltoni, lonchocarpus. Megacarpus and Hayden-; 

 ianus pass over the Wasatch Plateau into the edge of the Great Rasiu, 

 Only A. Geyeri and lentiginosiis are of general distribution, caused 

 evidently by winds from up the Colorado. A few species come in 

 from the north around the Uintas such as confertiflorus. pygma^us 

 and simplicifollus, but only the latter is a real immigrant as Hie 

 others have migrated out rather than in. A. calycosus has come in 

 from the Great Basin. A. tenellus has come down from the high 

 peaks. A. Utahensis and Purshii are evidently immigrants, as is A. 

 argophyllus. It is interesting to note the effects of certain ecolo- 

 gical factors on the development of certain species . Astragalus de- 

 speratus is normally a densely tufted plant from a woody crown and 

 about six inches high, with long leaves and many leaflets and long 

 peduncles having many densely racemose flowers about 1 cm. long. 

 This is when it grows in wide crevices in the sandstone rocks. When 

 It grows in loose sand areas on the rocks and near them it is 

 much the same but mostly prostrate in mats. When growing 

 In tight and narrow crevices which is the common state on bare rocky 

 knolls or eroded and gently sloping rocks it is reduced to a rosette 

 often only % inch wide with short leaves and few leaflets and short 

 peduncles with only a flower or two and a single mottled pod. The 

 flowers are 'then hardly larger than A. raontanus and broad, and the 

 general appearance is that of the tegetarius variety, the whole closely 

 resembling A. humilliraus but with few stems and not densely matted 

 in broad mats. 



On the Tropical part of the Navajo Basin annual Inflati come in, on 

 the sandy stretches. 



This Basin belongs in the second grand division. 



The Green River Basin of Wyoming is a little area with the 

 same badland soil as the upper Navajo Basin, but is far colder. Its 

 flora is peculiar, with several distinct forms, but in Astragali is 

 not worth mentioning except one form, A. Grayi, a derivative from A. 

 pectinatus. . Its climate is a mixture of the Atlantic and Pacific hu- 

 midity and rainfall. 



The northern Plains region has a meager Astragaline flora, be- 

 longs to the first grand division and is caused chiefly by wind 

 movement and the low rainfall and temperature of the trough along 

 the east base of the Rockies. 



The Columbia Basin is an Interesting croup of the Pacific grand 

 division of floras. Its factors are mountain isolation, snow cover 

 except in the center in winter, rather high spring humidity continuing 

 more or leys through the summer, and almost total absence of sum- 

 mer rains. This insures a copious spring flora, and a consplcuoua 

 grass cover but no sod. There is a limited alkaline area In narrow 

 stretches where few recullar Podo-sclerocarpl flourish. The gras* 

 region sujjports the Collini and Reventl-Arrectl. and some Argo- 



