SEED AND SEED SELECTION 37 



adulterants. What are the chief characteristics of alfalfa 

 seed? On accompanying pages are samples of Dure 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 are seen clearly illus- 

 trated herewith, under a magnification of five diameters 

 arranged for comparison in parallel rows. 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 

 amojig 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 difSculty in distinguishing 

 from alfalfa the seeds of Yellow trefoil and of Sweet 

 clover (Melilotus), which latter frequently occurs as a 

 weed seed, and possibly in some cases in sufficient quan- 

 tity to be suspected as an adulterant. By comparison of 

 the seeds of alfalfa with the two adulterants just men- 

 tioned, the resemblances and differences, in the case of 

 the three species, will become evident. In general the 

 seeds of Yellow trefoil are shorter and rounder than 

 those of alfalfa, the largest seeds of trefoil measuring 

 0,0629 inch wide by 0,0897 inch long; whereas the larg- 

 est alfalfa seeds measure 0*0653 inch wide by 0.1153 inch 

 long; so that the largest alfalfa seeds are a trifle wider 



