CHAPTER XIII. THE FRUIT AXD SEED. 



Fig. 356. 



plantlet, when they decay and disappear. Such cotyledons are 

 described as hypogeal, while those which rise above the soil are 

 called epigeal. 



Embryos like those of the Bean, because they possess two 

 opposite cotyledons, are called dicotyledonous. Not all embryos, 

 however, are constructed on precisely this plan. Some, as those 

 of Lilies, Sedges and Grasses, have the leaves alter- 

 nate from the start, and usually the lower one is 

 much the most highly developed, and being the 

 only conspicuous one, besides being folded about 

 the rest and concealing them from view, the em- 

 bryo is called monocotyledonoits. Fig. 356 repre- 

 sents the monocotyledonous embryo of Indian 

 Corn. The embryos of some other plants, partic- 

 ularly of many members of the Pine family, have 

 more than two cotyledons in a whorl — 

 sometimes as many as fifteen ; embryos 

 of this kind are sometimes described as 

 polycotyledonous. Fig. 357 represents 

 the germinating embryo of a species of 

 Pine. There are a few cases in which 

 the cotyledons are aborted or wanting. 

 Such embryos have been called acotyledonous. The seed 

 of the common Dodder contains an embyro of this 

 kind. There is much reason to believe, however, that 

 it was once dicotyledonous, for the affinities of that plant, 

 as shown by the structure of its flowers, are with Dico- 

 tyledons. The plant is, however, a parasite, and, doubt- 

 less, the loss of its cotyledons bears some relation to its 

 parasitic habits. Probably once, like its near relative, 

 the Morning-glory, it possessed foliage, and obtained 

 its living in a legitimate way, but having acquired the 

 parasitic habit (a habit degrading alike to plants, ani- 

 mals and men), and having no use 

 for foliage of its own, it lost its 

 leaves, and the degradation of 

 form came finally, even to affect the embryo and cause the loss of 

 its cotyledons. These probably were once highly developed and 

 did partial duty as foliage, as those of the Morning-glory still do. 



Fig. 357 



Fig. 356. — Monocotyledonous embryo of 

 the Indian Corn. 



Fig. 357. — Polycotyledonous embryo of a 

 species of Pine, Pinus Pinea. (After Sachs). 



