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, leptocarpus, 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, tI is possible that this is true of A. hypoleucus, A. 
amphioxys blooms as a winter annual but is a perennial, though 
short-lived. 
Most species have peduncles as long or longer than the leaves 
and in the upper axils. Very few have short peduncles with flowers 
nearly sessile in the axils, und 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 funereus which 
protect them from the summer heat; A. simplicifolius, sericoleucus, 
triphyllus, montanus, humillimus, Giiensis, and campestris which 
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 species 
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, nigrescens, 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 
soil. 
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 exce;t Uiose 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 scils 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, mega- 
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 densely with 
other plants have more slender stems, smaller leaves and larger 
flowers and pods. ; 
It is a commom 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 specially moist 
* 
