118 DISEASES OF FIELD & GARDEN CROPS. [OH. 



clover seed, although often brown, is smooth and shining, 

 with a minute scar or protuberance at one point of the 

 circumference at E, Fig. 48. At this point the radicle, 

 the first or elementary root of the plant, emerges at the 

 time of germination. This scar is almost invisible in 

 dodder seeds. When seen in section a clover seed mate- 

 rially differs from a dodder seed. The interior of the 

 clover seed shows the presence of cotyledons or seed- 

 leaves, as at Fig. 49, A, enlarged ten diameters ; and the 

 first rudimentary rootlet or radicle at B. The illustra- 

 tion at shows a clover seed after it has been planted 

 for three days or a week in moist sand. The testa, or 

 outer integument of the seed, has burst, and the first 



PIG. 49. 



Seeds of Perennial Bed Clover and Clover Dodder, seen in section, and 

 germinating. Enlarged 10 diameters. 



rootlet of the infant clover plant at D is descending to 

 the sand. Clover-dodder seed is engraved to the same 

 scale at E and F ; at E the seed is shown in section ; 

 there are no seed leaves, but the young plant within con- 

 sists of a simple thread, spirally coiled round a little 

 central mass of fleshy albumen. At the period of germi- 

 nation the thread emerges with a dilated end as at G, 

 and the granular coat of the seed frequently breaks up as 

 shown. If a germinating seed in this condition is trans- 

 ferred to a slip of glass and held before a strong light, 

 the spiral embryo will be seen through the cracked testa 

 as here illustrated. Sometimes the cotyledons or seed 



