3^0 



THE STRUCTURE OF ECONOMIC PLANTS 



ground as the hypocotyl elongates and straightens. The first 

 epicotyledonary leaf is simple and obcordate or orbicular with a 

 very slender petiole, while the second, third, and subsequent 

 leaves are trifoliate. (Fig. i6i.) 



The seedling axis is slender with a short first internode, but the 

 second one may elongate very greatly as the plant matures. There 

 are buds in the axils of the cotyledon as well as in the axil of each 

 foliage leaf, and these develop coincident with the growth of the 



C3P 



7 



Fig. i6i. Stages in development of seedling in Grimm alfalfa. 



primary axis to form a "crown." This term has been used by 

 Stewart (^9) to include the perennial portions of the stems of the 

 plant. 



Very commonly, there are three or sometimes four branches, in 

 addition to the primary axis, which form this characteristic crown. 

 When four develop, the fourth arises from the axillary bud of the 

 first trifoliate leaf, following the development of the other three 

 from the cotyledonary buds and that of the unifoliate leaf. (Fig. 

 i6i. A.') In the case of vigorously growing plants, additional 

 branches may arise from adventitious buds which occur near the 

 bases of the axillary branches, the first one usually developing 



