56 



The effects of humidity, other things being the same are shown 

 in the Columbia Basin. As we approach the Columbia Basin there 

 is a marked increase in spring and summer humidity though there is 

 less summer rainfall. The winter snows are deeper and the snow 

 cover is permanent through most of the region in the winter months, 

 which is a great protection to the vegetation. There is less alkali. 

 The species of Astragalus become more slender and with more woody- 

 roots. The Reventi-Arrecti and Collini prevail; there are some 

 Atrati, some Homalobi, and Podo-sclerocarpi, and a number of Argo- 

 phylli. No species have phyllodia-like leaves, few have broad leaflets 

 and most of these are folded and pubescent. The species are almost 

 exclusively perennial. It is a region of abundant spring flora, par- 

 ticularly grasses. 



The northern Plains along the trough of slight rainfall caused by 

 the Rockies has a humidity a little higher than the Coumbia Basin 

 and is wind swept throughout the year, and with a low temperature 

 There is a permanent snow cover except where elevations catch the 

 wind. There is a little alkali. These conditions have produced the 

 densely matted Homalobi and Triphylli with their scapose pedun- 

 cles hidden among the leaves and their narrow, thick and silvery 

 leaves and large and densely imbricated stipules. It is only in the 

 bottoms where the snow cover is not disturbed that the slender and 

 v'ariably erect species are found such as the Bisulcati and pectina- 

 tus in alkaline places, the slender Homalobi, Debiles and Hypoglot- 

 tides. 



The interior valley region of California s!m-ilates th'^ Arizona- 

 Death Valley region in its Tropical climate and extensive annual 

 flora, and some species are common to both regions, but the h'gi°r 

 humidity and winter rains have greatly increased the species and irii- 

 viduals. Here abound the Didymocarpi, and Leptocarpi. The 

 salt marshes have the annual A. Hornii and the remarkable perennial 

 A. pychnostachyus. It is a noticeable fact that nearly all Californian 

 Astragali have short pubescence closely appressed. 



The Coast region of California has a remarkable development 

 of the Inflati, along with a few Hamosi, in addition to the 

 annuals of the interior region. Its chief characteristics are high 

 temperature, high humidity (due to fogs) and no rainfall except in 

 winter. We therefore find no species with phyllodia, or stems with 

 leaf functions. There is a large development of leaf surface with 

 folded leaflets and slender stems. The Argophylli are mostly absent 

 and the Homalobi scarce, as are most other groups. 



In the Sierra region the Astragali are scarce in the forested 

 area. At the north A. accidens is found among the bushes, and 

 Californicus and inversus among the yellow pines. Higher up we 

 find A. Congdoni, Bolanderi and Hookerianus, mostly farther south, 

 but the soil is a very granular granite and not adapted to any vege- 

 tation, and so the general flora is meager. 



The Argophylli, plants of the lower mountain slopes with no per 

 manent winter snow cover, with plenty of spring humidity due to 

 rains or melting snows show a curious distribution. Inthe Columbia 

 region they develop a loose and cottony pubesence, narrow flowers, 

 and lax stem system. A. inflexus even attempts to become erect. 

 The Argophylli are normally caespitose and prostrate species. This 

 condition of the Columbia species is manifestly due to higher humidity 

 and light soil. As the group extends south along the Sierras in the 

 impoverished soil the same species become densely matted and often 

 only a few inches across, with very short stems, small leaves and very 

 small flowers and pods. At the foot of the monutains and out on 

 the mesas where it is much hotter and drier but the soil better 

 we have the magnificent A. coocineus and funereus far surpassing 



