342 



FRUITS AND SEEDS 



seed.) In some cases, as in 

 corn, the cotyledon may de- 

 velop into an absorbing organ, 

 drawing nourishment from the 

 rest of the seed. (See Figure 

 i 49 .) 



Usually a scar may be found 

 on the surface of a seed indi- 

 cating the point at which it 

 was attached to the ovary. 

 This scar may be readily found 

 in the bean. It is called the 

 hilum. 



When the seed is mature, 

 the embryo is usually differen- 

 tiated into the following parts : 

 cotyledons, hypocotyl (the word 

 means below the cotyledons), 

 and plumule (or epicotyl, that 

 word meaning above the cotyle- 

 (Study Figure 150 and 



Fig. 150. — Embryo and seedlings of 

 bean. The two large cotyledons 

 entirely fill the seed; there is no 

 endosperm. A, embryo removed dons). 

 from the testa; the colorless testa . 

 slips off easily after beans have been 1 ' s explanation.) 

 soaked in water. B, the embryo 

 split open ; it separates readily into 

 the two cotyledons, revealing the 

 rest of the young plant lying be- 

 tween them ; h, hypocotyl ; p, plu- 

 mule. C, young seedling, showing 



cotyledons, hypocotyl, plumule, and radicle ; the hypocotyl is the part of the 

 embryo below the attachment of the cotyledons ; the plumule is the bud be- 

 tween the cotyledons; it is sometimes called the epicotyl; its outer part 

 unfolds and forms the first true leaves ; the root part of the embryo, indicated 

 by the little rootlets arising from it, is called the radicle ; it is a part of the 

 hypocotyl. D, an older seedling showing the first internode (above the coty- 

 ledons), and the first true leaves; nourishment is still being drawn from the 

 cotyledons. 



F. Cotyledons and the Divi- 

 sions of Seed Plants. You 

 have noted that one of the 



