20 BULLETIN 428, U. S. DEPARTMENT OF AGRICULTURE. 
from Semipalatinsk, Siberia, and the last two from Orenburg, Russia. 
Root systems of similar character are found in Rhus glabra L., Am- 
brosia psilostachya DC., Cirsium undulatum (Nutt.) Spreng., Con- 
volvulus arvensis L., [pomoea leptophylla Torr., and numerous other 
species. The development of proliferating roots in certain forms of 
Medicago falcata presents a rather interesting situation from a 
taxonomic standpoint. So far as the writers are aware, there are no 
other species having two forms, one in which this character is present 
and the other in which it is absent. 
The tendency to produce rooting rhizomes permits the development 
of a much more extensive root system than is ordinarily found in 
Medicago sativa. It is characteristic of many of the roots of MJedi- 
Fig. 7.—Individual plant of Medicago falcata, S. P. I. No. 20717, typical of the forms 
included in Group I. 
cago falcata that they possess the ability to produce new plants if 
cut off at the surface of the ground or if they become exposed acci- 
dentally. 
GROUPS. 
A division of the forms of Jedicago falcata into groups may be 
made on the basis of several characters; for example, color, size, and 
abundance of flowers, type of pod and seed habits, foliage charac- 
teristics, stem types, and even root systems to a certain extent. From 
a strictly botanical standpoint a classification on one or more of these 
sets of characters would appear to be desirable, but the combinations 
of characters in the plants are such that a logical grouping along 
