20 



BULLETIN 428, U. S. DEPAETMENT OF AGKICULTUEE, 



from Semipalatinsk, Siberia, and the last two from Orenburg, Eussia. 

 Boot systems of similar character are found in Rhus glabra L., Am- 

 brosia psilostachya DC, Cirsium undulatum (Nutt.) Spreng., Con- 

 volvulus arvensis L., Ipomoea leptojjhylla Torr., and numerous other 

 species. The develoj)ment of proliferating roots in certain forms of 

 Medicago faZcata 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 sj^'stem than is ordinarily found in 

 Medicago sativa. It is characteristic of many of the roots of Medi- 



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. 



A division of the forms of Medicago 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 



