17 



A. desperatus belongs in the Argophylli. A. Drummondii. racemosus 

 and scopulorum belong in the Galegiformes. A. obcordatus and va- 

 riegatus (sparsiflorus) belong in the Sparsiflori. A. humistratus be- 

 longs in the Homalobi. A. distortus belongs in the Hamosi probably. 

 He creates Xylophacos to include Gray's Argophylli. 



PRESENT REVISION. 



The writer began his work on the revision of the genus in 189ij, 

 a year after the appearance of Sheldon's abortive "Preliminary List," 

 in the belief that no closet botanist could ever revise the genus pro- 

 perly, and with the intention to work out the genetic relationship 

 of all the North American species in the field. I had already spent 

 sixteen years in the field on the genus along with other flowerin? 

 plants, but with no intention to revise it. 



My first work was an examination of all the types in this 

 country and photographing them, which was the first work of that 

 kind in this country. Then some years were spent in a fruitless 

 attempt to follow Gray and Watson. When I had the genus about half 

 done the scheme utterly collapsed. The mass of genetic and ecologic- 

 al information accumulated in the field and the great amount of 

 material seen which embraced all to be found in all the leading her- 

 baria in the country, and the study of nearly every species in the field 

 compelled me to attempt a new classification. For a time the arch- 

 ing of the ventral suture offered much encouragement, but this also 

 broke down with a very few species. I then took up the genus 

 from an ecological and genetic view-point, making much of geogra- 

 phical proximity, and this led me out where I believe the genetic 

 relationship of all the species is no longer guess-work but an estab- 

 lished fact. These studies showed that the intrusion of the sutures 

 though valuable on the whole must not be relied on, nor the thick- 

 ness of the walls of the pods, nor the inflation. The differentiation 

 of the genus has gone along on other lines. 



The genus originated in the Temperate life zone in its colder 

 regions as is shown by the most primitive species the Homalobi, of 

 which very few are found in hot regions and all are perennials. 



I have tried to retain the old sectional names wherever this does 

 not cause confusion. The new sectional names are taken from the 

 leading species in the group. In subdivisions of sections, wherever 

 groups are well defined I have named them in the same way. 



That Astragalus is closest related to Oxytropis. Crotalaria and 

 Colutea is evident, but the Homalobi remind one much of Hosackia 

 pnd Lathyrus, the pods splitting and curling in the same way in 

 several species. 



I take the Homalobi to represent the lowest forms and A. cam- 

 restris the lowest species. From this an early offshoot is the 

 Triphylli presaged by the caespitose species A. simplicifolius and 

 carried much farther in A. montanus. These are Plains adaptations. 

 The Lotiflori represents another digression toward the inflated forms 

 represented in the lowest group the Debiles also an earlier offshoot 

 of the Homalobi and which reached considerable alteration in the 

 Inflati of the arid and variably alkaline and hot deserts, and in 

 the Sparsiflori of the more moist and sweet-soiled mountains whicli 

 group also passes into the Alpini of the high and Arctic regions. It 

 should be noticed that regions with deen snow produce thin-walled 

 ))ods. Regions with little or no snow and with a tendency to alkali 

 and a warm climate favor differentiation into thin-walled and in- 

 flated pods in offshoots of the Debiles. 



The Homalobi again branch into the CoHini which represents one 

 of the two great lines of differentiation. The Collini branch into the 

 Podo-sclerocarpi of the Columbia Basin and northern Great Basin 



