SEEDS AND SEEDLINGS. 



213 



last there is nothing but a thin whitish film covering the green 

 faces of the cotyledons. The endosperm has been gradually 

 absorbed by the germinating plant through its cotyledons and 

 used for food. 



Ariseema triphyllum. 



351. Germination of seeds of jack-in-the-pnlpit. — The 



ovaries of jack-in-the-pulpit form large, bright red berries with 



a soft pulp enclosing one to several 



large seeds. The seeds, are oval in 



form. Their germination is interesting, 



and illustrates one type of germination 



of seeds common among monocoty- 



ledonus plants. If the seeds are covered 



with sand, and kept in 



a moist place, they will 



germinate readily. 



Fig. 188. 

 Germination of castor-oil bean. 



352. How the embryo backs out of the seed. — The embryo 

 lies within the mass of the endosperm ; the root end, near the 

 smaller end of the seed. The club-shaped cotyledon lies near 

 the middle of the seed, surrounded firmly on all sides by the 

 endosperm. The stalk, or petiole, of the cotyledon, like the 

 lower part of the petiole of the leaves, is a hollow cylinder, and 

 contains the younger leaves, and the growing end of the stem 

 or bud. When germination begins, the stalk, or petiole, of the 

 cotyledon elongates. This pushes the root end of the embryo 

 out at the small end of the seed. The free end of the embryo 



