TWO TYPES OF PROLIFERATION IN ALFALFA. i 



In summarizing the observations and conclusions of the various 

 investigators it will be found that certain types of alfalfa, chiefly 

 those which are associated with hardiness and drought resistance, 

 produce underground stems and rhizomes; that these growths are 

 true stems having nodes, scales, and buds; that although sometimes 

 found several inches beneath the surface, they usually originate at 

 or near the crown, seldom below; that the rooting and nonrooting 

 rhizomes may result in new shoots and in some cases ultimately in 

 independent plants; that by virtue of their ability to store up water 

 and produce protected buds they constitute a drought-resistant and 

 hardy character of much value to the plant ; and that the rhizomes 

 in their various forms are more abundantly produced in Medicago 

 falcata and its natural and artificial hybrids with M. sativa than in 

 pure M. sativa. 



The rediscovery, if such it may be called, of stem proliferation in 

 alfalfa is of vast importance, especially to plant breeders, as it gives 

 them a tangible character with which to work in developing hardy 

 and drought-resistant strains. 



Field studies and correlation of characters. — In May, 1912, the 

 writers took up a general study of proliferation in Medicago falcata 

 with a view to determining the extent of its prevalence and variation 

 in the different types of that species. Although late spring is prob- 

 ably not the best season of the year in which to study this character, 

 the abundant material in the nurseries at Brookings and Highmore, 

 S. Dak., afforded an excellent opportunity for observation, especially 

 since the plants were growing in cultivated hills and most of them 

 entering into their fourth season of growth. 1 



A careful examination of the numerous forms of Medicago falcata 

 showed underground stems or rhizomes to be more prevalent and 

 better developed in the low-spreading, fine-leaved, fine-stemmed types 

 than in those more closely resembling M. sativa. However, not all 

 of the forms included in the low-spreading type exhibit tendencies 

 to produce new plants vegetatively. Some spread only over the 

 surface of the ground, the procumbent stems proceeding from fairly 

 compact and high-set crowns without becoming attached to the soil 

 at any point. It was extremely difficult in the case of certain pro- 

 cumbent types to determine whether proliferation was largely the 

 result of an inherent tendency of the plant or was induced to a 

 considerable degree by cultivation. Cultivation unquestionably is 

 in a measure responsible for rooting stems in the erect as well as 

 in the procumbent forms. This point was quite definitely demon- 



a The plants wore grown in the nursery at Brookings and transplanted in hills at 

 Highmore in April, 19.10. It is a well-known fact that the pruning incident to trans- 

 planting large alfalfa plants affects the development of the taproot. The above-mentioned 

 plants, however, were so small at the time of transplanting that little change in this 

 respect is believed to have been produced. 

 [Cir. 115] 



