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 

 hirge 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 Wetherilli. 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- 

 shnped 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 piains of Nevada and adjacent Oregon, and the cosmopolitan 

 A. lentiginosus, at least as far as tlie 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 Ps 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- 

 florus 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 

 eperiocarpus 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 southw-ard, 

 the other in the Green River Wyoming drainage. All these have 

 ehort 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 



