MEDICAGO SATIVA 



3ZI 



between the branches arising from the buds in the axils of the 

 cotyledons. Several buds may develop from any point in the 

 circumference of the crown stem at this level, or even higher up on 

 the axis when the plants have become embedded in the soil. (Fig. 

 i6i, 5.) 



In very large crowns which have many small stems, it appears 

 that these arise in part adventitiously and in part from buds in the 

 axils of bracts and basal leaves. Jones (i 5) has pointed out that the 

 behavior of the plant in regard to the development of the crown 



A B 



Fig. 162.. A, symmetrical crown of a hardy alfalfa plant at end of its first winter : a, first 

 seedling stem; b and b' , stems from a.xils of cotyledons; c, stem from axil of unifoliate leaf; 

 d, stem from axil of first trifoliate leaf; e, first bud from base of crown, arising between stems 

 from axils of cotyledons and opposite the stem from the lowest seedling bud : B, crown and 

 portion of tap root of an uninjured alfalfa plant from a 4-year-old field at Madison, Wisconsin. 

 (After Jones, ]our. Agr. Rw.) 



is variable, depending upon the variety, the vigor of the plant, and 

 environmental conditions. Where the seedling is buried deeply, 

 the first branches of the crown may arise from axillary buds higher 

 up on the primary axis; and where a plant after forming a crown is 

 buried more deeply, a new crown may form higher up. No buds 

 arise from the root portion of the axis in cases where it may become 

 exposed. 



The IPrimary Root. — The stele of the primary root is triarch 

 or rarely tetrarch. The protoxylem abuts the pericycle and the 

 primary xylem is differentiated centripetally until a continuous 

 xylem strand is formed. The number of protoxylem elements in 

 each arm is usually limited to three or four annular and spiral 



