SEED AND SEED SELECTION 37 



indeed, of complete or almost complete substitution of 

 Yellow trefoil for alfalfa seed have come to the writer's 

 attention within the past year. It is important, there- 

 fore, for farmers to know the characteristic marks of 

 distinction between the seed of alfalfa and of its chief 

 adulterants. What are the chief characteristics of alfalfa 

 seed? Facing page 13 are samples of pure alfalfa 

 seed, photographed under a magnification of five diam- 

 eters. It will be noted that seeds of three general types 

 exist : ( i ) A kidney-shaped type, marked 'a' in the illus- 

 tration; (2) a type in which one end terminates in an 

 acute wedge, marked *e' ; and (3) a type that is round 

 or nearly so, marked 'b'. These types clearly illus- 

 trated, arranged for comparison in parallel- rows are 

 shown opposite page 44. See also page 27. It should be 

 noticed that type 2 is the most characteristic and frequent, 

 and that the perfectly round type is extremely rare. This 

 angular slant toward one tip of the seed is found nowhere 

 among any of the adulterants. Neither does the kidney 

 shape of seed occur, except in Bur clover; and, in that 

 case, the difference in the size of the seeds of the two 

 species is sufficient to distinguish them, in most instances. 

 "It is when we consider the round or roundish type 

 of alfalfa seed that there is difficulty in distinguishing 

 from alfalfa the seeds of Yellow trefoil and of Sweet 

 clover (illus. opp. p. 26), which latter frequently occurs 

 as a weed seed, and possibly in some cases in sufficient 

 quantity to be suspected as an adulterant. By comparison 

 of the seeds of alfalfa with the two adulterants just men- 

 tioned, (p. 26) the resemblances and differences of 

 the three species will become evident. In general the 



