134 



WEEDS OF THE FARM AND GARDEN 



radicle, or true root ; the caulicle, or stem ; and the cotyledons. 

 When there is one cotyledon the plant is monocotyle- 

 donous, when two it is dicotyledonous, when three or 

 more, polycotyledonous ; the plumule rises from the cauli- 

 cle. In germination, the cotyledon or cotyledons may re- 

 main in the seed, in which case they are said to be 

 hypogaeous, as in the pea; when they are pushed out, as 

 in the bean, they are epigaeous. 



Seeds may be smooth, as in the bean ; rough, as in corn- 

 cockle; they may have a thin membrane growing out 

 from the surface, in which case the seed is said to be 

 winged. 



Fig. 85. 



Fig. 84. 



Fig. 86. 



Fig. 84. Squash seed germinating. Root below and cotyledons push- 

 ing out: pp, pumpkin peg holding the testa. (C. M. King.) 



Fig. 85. Cross section of buckwheat "seed," an achenium: e, wall 

 of ovary, inner line represents the testa. Embryo with two cotyledons 

 surrounded by the endosperm; seed albuminous. (C. M. King.) 



Fig. 86. Cross section of date seed: en, hard and horny endosperm, 

 embryo small in lower part of seed. Seed albuminous. (C. M.King.) 



Fig. 87. A longitudinal section of kernel of corn; an albuminous seed: 

 ce, endosperm; pi, plumule; sc, scutellum; c, caulicle; pr, primary 

 root; h, point of attachment of kernel to cob; rs, root sheath. The 

 darker portion represents the endosperm, light portion embryo or germ. 

 (C. M. King.) 



