20 
western Arizona and near California, A. insularis on desert islands 
of Lower California and A. triflorus in the sandy places from Colo- 
rado to central Mexico where there is little alkali. A. pychnostachyus. 
in the salt marshes of the California bays, A. Hornii on the salt flats. 
of the San Joaquin and southward, and A. scalaris an aberrant 
thing from the barrancas of Chihuahua. Among the single celled and 
large podded forms A. subcinereus and pictus grow with running 
roots in sandy sagebrush regions of Colorado to Utah and Arizona. 
A. Wardi, serpens and nutans grow from stout roots in sagebrush 
regions of southern Utah to adjacent Nevada. A peculiar group of 
seacoast species inhabits the California-Mexican region such as A. 
vestitus, Pomonensis. Crotalariae, Miguelensis and Magdalenae. 
Another more inland group but near the other is A. macrodon and 
Douglasii. Large podded forms of the Grand Canon region are A. 
allochrous and Wetherili. All these are, except the last, plants 
with sessile pods. Balloon-shaped and variably stipitate plants are 
the diminutive A. jejunus of the Uintas, A. Cusickii of the lower 
Snake river drainage, and A. Hookerianus of the Sierras which 
comes close to A. Cottoni. Another quite distinct group and connected . 
with the Collini is A. oxyphysus, trichopodus and capillipes which 
belong in the southern California region and are related to the bal- 
loon-shaped section. Plants with large and stipitate but not balloon- 
shaped pods are A. leucophyllus, curtipes, leucopsis, and belong in 
the coast region of California, These all have no joint to the stipe. 
Plants with jointed stipe and large pods are A. lutosus of the dry 
ledges of western Colorado, A. megacarpus of the desert clay bad 
lands of Wyoming and Utah. A. oophorus and Bechwithii of the 
sagebrush plains and hills of Utah to Idaho and Nevada. Plants with 
variously 2-celled pods are A. triquetrus and Craigi of the Sage- 
brush plains of Nevada and adjacent Oregon, and the cosmopolitan 
A. lentiginosus, at least as far as the western plateau region goes, 
not extending much into Mexico. 
7. Lotiflori. This group would naturally be placed as a branch 
of the Debiles next the Sparsiflori, and may possibly belong there. 
But I prefer to place it as an offshoot of the Homalobi verging to- 
ward the Argophylli and near to the Atrati with which it seems re- 
lated. The rather fleshy pods variously 2-celled would place it here 
A. Mohavensis belongs in the rocky gulches of tne Death Valley 
region, and A. circumdatus in the Lower California region, accum- 
bens (procumbens) on the mesas of northern New Mexico, and A. loti- 
fiorus on the Plains from Wyoming to- Texas. 
8. The least modified group of the Homalobi in its beginning is 
the Collini, the pods being Homalobous but the flowers decidedly 
modified in the first three species A. Tweedyi, collinus and porrectus. 
Then the pods themselves become fleshy and inclined to corrugated 
and falcate in Gibbsii, which tendency is still more accentuated in 
speriocarpus and Alvordensis. All belong in the Columbia Basin drain- 
age and vicinity, in soil not very alkaline. 
9. Podo-sclerocarpi. This branch of the Collini shows a lengthen- 
ing of the flowers, and expansion and lengthening of floral rachis 
a reduction of the leaves toward phyllodia and thickening of tissue 
to suit the alkaline conditions in which it grows, The pods become 
more fleshy and rapidly differentiate. It is almost exclusively a 
Great Basin group of the alkaline plains. A. Toanus of the border 
land of Utah and Nevada is the lowest. A. pectinatus and Gray 
form a close group, the one on the Plains from Assiniboia southward, 
the other in the Green River Wyoming drainage. All these have 
short fleshy, sessile and little differentiated pods, but modified leaves 
Here branch off the Preussii, . Then comes A. Casei, pterocarpus, 
and tetrapterus with doubly falcate and elongated pods inclined to 
stipitate and much modified. These all belong to the Great Basin 
and A. tetrapterus extends beyond to the drainage of the Virgin river 
and the Colorado near and in Utah. A. Casei keeps close to the 
