“Bur clover as an adulterant is probably not so frequently 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 approximate each other in size, but the average Bur clover seeds measure 0.0604 inch by 0.1188 inch, as compared with an average for alfalfa of only 0.0582 inch by 0.0944 inch. “So far as the plants of Yellow trefoil and Bur clover are concerned, they are easily distinguishable from alfalfa. Both are of lower growth, as a rule, than alfalfa. Both have wider leaflets, which, in Bur clover, are like broad, inverted wedges. The flowers of these plants are yellow, and are borne in scanty clusters. The pods are wholly unlike those of alfalfa. Alfalfa has a spiral pod of two or three turns (p. 32), containing as many as five or six seeds. Yellow trefoil has a straight pod (p. 32), containing but one seed. Bur clover has a coiled pod (p. 33), but covered with bristly projections that give the plant its name. Where adulteration or substitution is practiced, some of the pods are very apt to occur in the bulk seed, and they can then easily be identified and distinguished from those of alfalfa. “Seed of Sweet clover seems to occur frequently in western-grown alfalfa seed (p. 26). Sweet clover (illustrated in this book) grows to a height frequently of from four to six feet, bearing small, white flowers on slender spikes three or four inches long. Unfortunately, and unlike Yellow trefoil and Bur clover, Sweet clover is generally rejected by stock. On this account, it is a plant of no generally established value for hay or as pasture, although, in some instances, it is successfully used. The seeds of Sweet clover are of a golden yellow when ripe; those of alfalfa, trefoil and Bur clover being greenish yellow. The seed coat of Sweet clover seed is covered with minute elevations, while alfalfa seed is smooth. The seeds of Sweet clover (p. 26) are rounder and plumper than those of alfalfa, and have a very pronounced groove between the main body of the seed and the ridge which marks the location of the rootlet of the young plant within. It is this ridge that in alfalfa seeds runs off, as a rule, in a marked slant, but which in both trefoil and Sweet clover, especially in the latter, forms a well-rounded curve to the tip of the seed. No pointed or kidney-shaped seeds are ever seen in Sweet clover. (See illus. opp. p. 26.) A COMMON WEED IN IMPORTED ALFALFA SEED “It remains to mention the most common weed found in imported alfalfa seed--the English or Ribbed plantain, or, as it is more generally called in the West, Buck-horn or Rib grass. It is a difficult weed to eradicate, lots of seed containing any noticeable percentage of it should be rejected. (See illus. opp. p. 13.)