Astragalus and its segregates as represented in Colorado 



Per Axel Rydbekg 



Linnaeus had two genera, Astragalus and Phaca, the former 

 with a 2-celIed, coriaceous or membranous pod and the latter 

 with a I -celled, papery pod. As more species have become 

 known these characters do not hold, as there are many species 

 which have the pods partly 2-celled, and the texture of both the 

 I -celled and 2-celled pods varies. The only reasonable ways to 

 treat these two genera, are to merge them into one or to divide 

 them into several The latter was tried by Torrey and Gray in 

 their flora. When still more species became known, Dr. Gray saw 

 that he had to propose a number of genera in order to be consis- 

 tent, gave the method up, and merged all the species into As- 

 tragalus. He was followed by Dr. Watson, In the Old World 

 the segregation was begun by Medicus, and continued by Opiz, 

 Fourreau and Steven. The latter proposed not less than 24 new 

 genera. It seems that these should cover all the forms that have 

 been included in Astragalus^ but this is not the case. In the Old 

 World, the completely 2-celIed series is best represented, but in 

 America the i -celled or incompletely 2-celled forms are predomi- 

 nant. The segregation into several genera was renewed in Dr. 

 Britton's Manual and carried somewhat further in Dr. Small's. 

 The Colorado genera and species may be disposed as follows ; 



Key to ilie %^ enera 



* 



Leaves pinnate or unifoliolate. 



Pods a-celled, with a perfect partition. 



Pods fleshy, indehiscent or very tardily dehiscent. I* Geofrumnon. 



Pods membranous, leathery or woody, dehiscent. 



Pods not inflated. 



Pods ovoid or oblong, rarely almost didymous, terete or flattened vertically, 



leathery or woody. 2. Astragalus. 



Pods linear, more or less flattened laterally, membranous. 



3, Hamosa. 



Pods %XxQTig\y inflated, papery. 4- Cystium, 



rudimentarv 



Lowe 



section ; pods membranous, rarely leathery. 5- TiUM. 



657 



