ANGIOSPERMS 



237 



FIG. 228. Seed of violet, one figure show- 

 ing the hard testa, the other the em- 

 bryo (young sporophyte) that has 

 developed from the oospore. After 

 BAILLON. 



from the peculiar character of their embryos. In one 

 division the root is developed at one end of the embryo 

 and the single cotyledon at 

 the other end, the stem 

 coming out on one side. In 

 the other division the root 

 is developed at one end of 

 the embryo and the stem at 

 the other end, two cotyle- 

 dons coming out on oppo- 

 site sides just behind the 

 stem tip. Therefore, the 

 first division is called Mono- 

 cotyledons (one cotyledon), 

 and the second is called Di- 

 cotyledons (two cotyledons). There are many other differ- 

 ences between Monocotyledons and Dicotyledons, but this 

 difference between the embryos has been selected to form 

 the names. 



The embryos of Angiosperms differ much as to the com- 

 pleteness of their development within the seed. In some 

 plants the embryo is merely a mass of cells, without any 

 organization of root, stem, or leaf. In many plants, on 

 the other hand, the embryo becomes highly developed, 

 showing all the principal organs and the plumule con- 

 taining several well-organized young leaves (Chapter V). 



142. Seed. The seed is evidently an ovule (sporangium) 

 containing a female gametophyte which has developed a 

 new sporophyte (embryo). This complex structure is 

 invested by the hard seed-coat, and is a protected resting 

 condition of the plant. 



The seed-coat (testa) in Angiosperms is exceedingly 

 variable in structure and appearance. Sometimes it is 

 smooth and glistening, sometimes pitted, sometimes rough 

 with warts or ridges. In many cases prominent append- 



