29 



with few exceptions are delicate and short-lived with delicate stems, 

 small flowers and pods, and quick maturing, produced by the peculiar 

 climate of the Tropical plains of the Arizona-California region and 

 extending into the Lower Temperate life zone, such as A. Nuttallian- 

 us, leptccarpus, Didymocarpi, etc. Several of these annuals in the 

 Mexican region start in the meager moisture of the spring and 

 make a growth sufficient to mature pods and then rest in the dry 

 season without dying out and in the fall rains grow vigorously and 

 bloom again more copiously, even having a woody old stem which 

 makes them seem like bienniels or perennials, and for this reason 

 we do not know yet what are truly annuals, among the higher 

 groups. A. Nuttallianus is known to start in the fall and bloom as a 

 winter annual, tl is possible that this is true of A. hypoleucus. A. 

 amphioxys blooms as a winter annual but is a perennial, though 

 Bhort-lived. 



Most species have peduncles as long or longer than the leaves 

 and in the upper axils. Very few have short peduncles with flower* 

 nearly sessile in the axils, and concealed pods. Very few have 

 the internodes longer than the leaves. Very few leaves persist in 

 winter and those which do are woolly or hairy and act as a protec- 

 tion to the roots, such as A. Utahensis, coccineus and fanereus which 

 protect them from the summer heat; A. simplicifolius, sericoleucus, 

 triphyllus, montanus, humillimus. Gilensis, and campes,tr(is v.hich 

 along with very condensed stems and large stipules protect them 

 from changes in temperature in winter and spring. Only those 

 alpine plants are thus protected which grow on gravelly or rocky 

 places where winter's snow is liable to be blown off. 



As a rule there is no crowding with other plants, and specie* 

 of Astragalus do not grow together. Exceptions to this are A. Nut- 

 tallianus which frequently grows among dense patches of other an- 

 nuals, A. didymocarpus , tener, leptocarpus, algrescens, Rattani and 

 Lindheimeri have the same and then become erect, though all 

 naturally are depressed to prostrate. 



The struggle for existence is purely one against climate and 



BOil. 



There is no evidence that any Astragali grow only on a lime 

 soil, or an iron soil or any other particular kind of soil chemically 

 speaking oxceit t'l-jse with active alkalies and acid. The plants 

 of acid soils are the Alpini and the like, growing in decomposed 

 vegetable humus. The plants growing only in actively alkaline soils 

 (this is soils with 1 per cent or more soluble alkalies containing 

 some carbonate of sodium) necessarily grow in clay soil in the bot- 

 toms of alkaline valleys. Such plants are A. pectinatus, Grayi, Toa- 

 nus. and nearly all of the Podo-scleroscarpi, and some of the Preussii 

 such as asclepiadoides, Pattersoni, sabulosus, ampullarius, mc;;a- 

 carpus. 



Very seldom do we see any species of Astragalus growing in 

 large patches, an exception to this is A. andinus, agrestis, bisulcatus. 

 Canadensis. 



Practically the only perennial species that come into competition 

 with other species by crowding are the Alpini, Debiles, Hypoglotti- 

 des, and in these groups there is no evidence of any differentiation 

 due to crowding. The annual species when growing dens^y with 

 other plants have more slender stems, smaller leaves and larger 

 flowers and pods. 



It is a common thing for the flowers of Astragali to vary greatly 

 In size according to the humidity. Where the season is particularly 

 dry the flowers are often almost rudimentary, where epecially moist 



