SEED AND SEED SELECTION 39 



not SO great as the differences found on comparing the 

 largest and the smallest seeds of the two species, the 

 average for the trefoil being 0.0574 inch by 0.0799 inch, 

 and for alfalfa 0.0582 inch by 0.0944 inch. So it will be 

 seen at once that while trefoil seeds as a rule are smaller, 

 shorter and rounder than those of alfalfa, the rule is 

 transgressed by many individuals. We must, therefore, 

 turn to the form and general outline of the seed. A 

 farmer can detect at once an attempt to substitute wholly 

 Yellow trefoil for alfalfa seed by the fact that in no case 

 will the kidney-shaped or the regular-pointed types of 

 seed be found in trefoil, whereas these always occur in 

 alfalfa. (Illustrated opp p. 26.) 



"In the more common cases, where adulteration rather 

 than complete substitution is practiced, detection is more 

 difficult — is practically impossible, in fact, without the 

 aid of a lens or magnifying glass having a power of 

 about fifteen diameters. There are many seeds of tre- 

 foil which can scarcely be distinguished from certain 

 rounded seeds of alfalfa. Generally, however, the trefoil 

 seed has a little projection or "beak" on the middle line of 

 the seed, just back of the scar marking where the seed 

 was attached to the pod. This is rarely found in alfalfa. 



"Bur clover as an adulterant is probably not so fre- 

 quently used as Yellow trefoil, since the larger size of 

 its seed renders detection easy. Were it not for this fact, 

 Bur clover would be a most effective adulterant, because 

 its seeds resemble those of alfalfa more closely than do 

 those of Yellow trefoil. There are, of course, smaller 

 seeds of Bur clover and larger seeds of alfalfa that ap- 

 proximate each other in size, but the average Bur clover 



