[From the BULLETIN OF THE TorREY Boranicat CLup, 32: 657-668. 1906.] 
Astragalus and its segregates as represented in Colorado 
Per AXEL RYDBERG 
Linnaeus had two genera, Astragalus and Phaca, the former 
with a 2-celled, 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 
1-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-celled series is best represented, but in 
America the 1-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 the genera 
Leaves pinnate or unifoliolate. 
Pods 2-celled, with a perfect partition. 
Pods fleshy, indehiscent or very tardily dehiscent. 1. GEOPRUMNON. 
Pods gerne leathery or woody, dehiscent. 
Pods not i 
Pods sae or se rarely almost didymous, terete or gion vertically, 
leathery or AGALUS, 
Pods linear, more or Mean flattened laterally, membranous. 
3. HAMosA. 
Pods strongly inflated, papery. 4. CYSTIUM. © 
Pods I-celled, the partition, if any, rudimenta 
Lower suture strongly intruded, making the nr sagittate. or obcordate in cross- 
section ; pods membranous, rarely leathery. 5. TIUM. 
657 
