424 FOE AGE PLANTS AND THEIR CULTURE 



FIG. 47. Seeds of sweet clover, a, 

 seeds showing variation in form and size ; 

 b, natural size of seeds ; c, a pod of sweet 

 clover. 



509. Seed. The seeds of sweet clover (Fig. 47) are 

 yellowish brown, much like those of alfalfa, but the sur- 

 face is duller and slightly uneven. By crushing, the 

 vanilla-like odor of cumarin is evident, at once distin- 

 guishing it from all 

 similar seeds except 

 other species of Melilo- 

 tus. Commercial seed 

 usually has a high de- 

 gree of purity and 

 should approximate 

 100 per cent, The 

 germination, however, 

 is very variable on ac- 

 count of " hard " seed. 

 In 22 southern-grown 

 samples, the average 



proportion of hard -seed was 60 per cent, and in an equal 

 number of northern-grown samples, 43 per cent. Im- 

 ported seed showed but 12 per cent hard seeds in 28 

 samples. The probable explanation of the better quality 

 of the European seed is that most of it was one year old 

 or more. The seed is reported to have remained alive in 

 some cases for 77 years. According to Werner, one pound 

 contains 235,000 seeds. 



510. Related species. Various other species of M eli- 

 lotus have been more or less utilized agriculturally, includ- 

 ing M. officinalis, M. indica, M. altissima, M. gracilis, 

 M. speciosa and M. ccerulea. The first two are abundantly 

 and the third sparingly introduced into America. The 

 last is really a species belonging to Trigonella. 



Melilotus officinalis, official melilot, is a biennial yellow- 

 flowered species. It is about two weeks earlier than 



