A number of different strains of white sweet clover are to be found in the average field, but most of them are not as marked or as conspicuous as the different strains of red clover. The principal differences between strains of sweet clover are in leafiness, habit of growth, and date of blooming. [Illustration: Fig. 4.--Buds produced on the crown of a sweet-clover plant at the end of the first season's growth. These buds will produce the first crop the second season.] Occasional plants are especially heavy seed producers and bear many pods containing more than one seed. Other plants bloom earlier than the average date for white sweet clover, and it may be possible by selecting such strains to find one which matures early enough to produce two crops a season at high altitudes in the northern sections of the United States. Fields of an exceptionally early blooming strain were found in Illinois, Iowa, and North Dakota in the summer of 1916. The plants were different in type of growth from the ordinary white sweet clover, being most conspicuous from the fact that they were in bloom during the first week of June, which is at least three weeks earlier than the ordinary species should bloom in these localities. [Illustration: Fig. 5.--Root of white sweet clover (on the left) and of biennial yellow sweet clover (on the right). These roots were collected on October 28, 1915, at Arlington, Va., from adjacent plats seeded to cuts and sweet clover on April 10, 1915. Note the difference in the size of the roots. Tubercles are present on the right-hand side of each root.] An annual white-flowered sweet clover was found in several localities in the fall of 1916. The seed which produced these plants was grown in Alabama. These plants resembled _Melilotus alba_ in most respects except that they were strictly annual. They flowered and matured seed abundantly in South Dakota and North Dakota. It has not been determined whether this is a distinct species or merely an annual strain of the species mentioned. BIENNIAL YELLOW SWEET CLOVER.