376 



A TEXTBOOK OF BOTANY [Ch. VIII, 2 



Fig. 271. — Ex-albu- 

 minous seed, of Apple ; 

 X4. 



The embryo, show- 

 ing clearly the coty- 

 ledons and hypocotyl, 

 fills completely the 

 space inside the seed 

 coats. 



appendage which contains nutritive substances apparently 

 having a functional meaning in connection with dissemi- 

 nation (page 356). 



Seeds show many structural relations 

 with the ovules from which they develop, 

 precisely as do fruits with their ovaries, 

 though it must not be inferred that all 

 such features in seeds and fruits are 

 simple persistences of ovule or ovary 

 characters. It is equally possible that 

 some have originated in seeds or fruits 

 and worked back in evolution into ovules 

 and ovaries. 



Every seed shows on its coat a tiny 

 pit, sometimes differently colored, which 

 is the persistent though now sealed 

 micropyle, or opening through which 

 the pollen tube entered the ovule (page 278). This of 

 course has no connection with the much larger scar, called 

 the hilum, left where the seed breaks away from its stalk 

 (Fig. 272). Where ovules are turned over on their elongated 

 stalks, which are grown to the coats (page 

 272), the arrangement persists, in the seeds, 

 which show a marked ridge, or raphe. The 

 position of the chalaza of the ovule often 

 is manifest in a marked chalazal angle in 

 the seed. 



Appendages, when present, whether hairs, 

 plumes, hooks, or others, are direct out- 

 growths from the seed coat, and have 

 obvious function in connection with dis- 

 semination, as already discussed (page 356) . 

 Outgrowths of the same kind occur often a * , the , top * s the 



. . . . chalazal angle. 



on ovaries which contain on y a single seed, 



in which case one can tell only by dissection whether an 



ovary wall is present or not. 



Fig. 272. — Seed 

 of a pansy ; X 5. 



Below and facing 

 to the left is the 

 hilum ; at the point 

 (invisible) is the 

 micropyle ; along 

 the side on the left 

 is the raphe ; and 



