760 IOWA DEPARTMENT OF AGRICULTURE 



TESTING WINTER RAPE SEED. 



Popular tests of rape seed are not likely to be wholly satisfactory be- 

 cause of the difficulty in identifying with certainty the seeds of the 

 different kinds of rape and the closely allied mustard weeds. Seed of the 

 more important winter, or Essex, rape may generally be recognized by 

 the relatively large size of the individual seeds (somewhat larger than 

 those of summer rape or of turnip), by their steel-black color, and their 

 roundness, allowing them to roll readily on a plane surface. Summer 

 rape seeds are mostly smaller, consisting of a mixture of black and reddish 

 seeds, some of the black seeds being distinctly pitted, or nearly all the 

 seeds reddish. Some lots of seed, particularly of summer rape, are 

 adulterated with seed of English charlock. As a rule the charlock seeds 

 may be distinguished by their smaller size, more nearly spherical form, 

 their smoother surface and by the presence of mature reddish or brown 

 seeds with the black ones. Some lots of rape seed are heavily adulter- 

 ated with seed of Indian mustard. These seeds are readily recognized 

 by their uniformly reddish-brown color and by the netted or pitted sur- 

 face as seen under a magnifier. The purity of winter rape should be 

 99 per cent or higher, the viability as high under a test of two or three 

 days' duration. A miscellaneous series of weed seeds, most of which are 

 previously described and figured, is likely to appear in poorly cleaned 

 grades of rape seed, particularly the summer variety. 



TESTING VETCH SEED. 



A popular test of vetch seed consists chiefly in distinguishing the seed 

 of hairy (winter) vetch and that of spring vetch, and determining the 

 viability. 



Winter vetch seed consists of nearly spherical, steel-black seeds show- 

 ing some variation in size. The seed is distinguished from other kinds 

 by its characteristic seed-scar which is oblong-oval with a whitish slit 

 through the center. A small protuberance (the chalaza) of the seed coat 

 is located nearly the length of the scar distant from the narrower end of 

 the scar. 



Fig. 32. — Seeds of three kinds of vetch; a. Winter (or hairy) vetch; b, spring 

 vetch; c, wild vetch (Vicia hirsuta). (Enlarged and. natural size.) 



Seeds of spring vetch represent several varieties and thus are variable 

 in size, form and surface. The characteristic scar is wedge shaped with 

 a slender, black slit through its center, the slightly raised margins of 

 the slit usually being light colored. The usually distinct chalaza, as a 

 rule, is about half the length of the scar distant from the narrower 



