8 CIRCULAR NO. 115, BUREAU OF PLANT INDUSTRY. 



strated in experiments conducted at the Arlington Experimental 

 Farm during- the past season. 



In a great many cases where stem proliferation is developed to 

 a considerable degree the center of the plant dies out, leaving that 

 portion of the crown quite devoid of shoots. A similar condition 

 is found in the true grasses, especially in forms of Festuca rubra and 

 other fine-leaved fescues. Many explanations of this condition have 

 been based on erroneous conclusions; in other words, it has been 

 argued that underground stems and rhizomes by virtue of their 

 ability to produce new growth keep these old plants alive, even after 

 the original crown has died. As a matter of fact, the barrenness 

 of the old crown is probably due in most cases to unfavorable con- 

 ditions for the development of buds or new growth in the center of 

 the clump. Where the original plant is grown in a crowded condi- 

 tion or in a condition not conductive to spreading, the center remains 

 productive for an indefinite period. The fescues already referred 

 to behave almost exactly in this manner. Barren centers are found 

 very frequently in procumbent types, while in the semierect or up- 

 right plants the tendency is not so common. 



ROOT PROLIFERATION. 



The brief studies at Brookings and Highmore developed nothing 

 particularly new regarding the type of proliferation heretofore 

 described, but tended only to confirm the conclusions of other investi- 

 gators. The studies disclosed, however, what is thought to be a type 

 of proliferation heretofore undescribed as occurring in alfalfa — a 

 type wherein new plants are produced from true lateral roots 4 to 

 12 inches, rarely more, beneath the surface and running almost 

 directly parallel with it. 1 These proliferous roots apparently are 

 given off from any portion of the branching taproot within the limi- 

 tation of the depths above indicated. At irregular intervals along 

 the lateral roots, swellings occur, usually about twice the diameter 

 of the roots and three-fourths of an inch to 1-j- inches in length. 

 (See figs. 2 and 3.) Upon these swellings buds appear, some of which 

 give rise to new plants, while many remain undeveloped. 2 Fibrous 

 roots are rather sparingly produced from the lateral proliferous 

 roots, and in many instances the swellings are devoid of them ; in 



1 Hitchcock, A. S., and Clothier,' G. L. Fifth report on Kansas weeds — Vegetative prop- 

 agation of perennial weeds. Kansas Agricultural Experiment Station, Bulletin 76, 23 p., 

 12 pi., 1808. Clothier, G. L. Root propagation of Ipomoea leptophylla. Botanical Gazette, 

 v. 25, p. 52-53, illus., 1898. These articles discuss vegetative reproduction hy true roots 

 in Rhus glabra. Ambrosia pssilostachya, Cnicus undnlatvs, Convolvulus urn axis, and 

 Ipomoea leptophylla. 



- In this type of proliferation it will be noted that definite provision is apparently 

 made by the lateral proliferous roots for the production of new plants. There is a mate- 

 rial difference in this respect from the case in stem proliferation noted by Oliver, where 

 new shouts arise from the taproot appreciably below the crown. 



[Cir. 115] 



