THE SEED. 



119 



of the young plant. The nutritive matter deposited in the seed for the 

 early sustenance of the germinating embryo is found more abundant 

 in the cotyledons in proportion as there is less of it in the albumen, 

 often wholly in the albumen (wheat), again all absorbed in the bulky 

 cotyledons (squash). 



595. THE NUMBER OF THE COTYLEDONS is variable, and upon this 

 circumstance is founded the most important subdivision of the Phseno- 

 gamia, or Flowering-plants. 



596. THE MONOCOTYLEDONS are plants bearing seeds with one coty- 

 ledon, or if two are present, one is minute or abortive. Such plants 

 are also called Endogens, because their stems grow by internal accre- 

 tions ( 716). Such are the grasses, the palms, Liliaceae, whose leaves 

 are mostly constructed with parallel veins. % 



597. THE DICOTYLEDONS are plants bearing seeds with two cotyle- 

 dons. These are also called Exogens, because their stems grow by ex- 

 ternal accretions, including the Bean tribe, Melon tribe, all our forest 

 trees, etc. These are also distinguished at a glance by the structure of 

 their leaves, which are net-veined ( 258). 



598. MORE THAN TWO COTYLEDONS. The Pine and Fir have seeds 

 with several cotyledons, while the dodder is almost the only known 

 example of an embryo with no cotyledon. 



467 463 469 



j 



466, Dicotyledonous (Bean). 467, Monocotyledonous (Wheat). 463, Polycotyledonous (Pine). 

 469, Acotyledonous (zoospore of one of the Confervae). (;, ?*, r, radicle ; p, />, p, plumule ; c, c, c, 

 cotyledon ; a, albumen). 



599. THE POSITION OF THE EMBRYO, whether with or without albu- 

 men, is singularly varied and interesting to study. It may be straight, 

 as in cat-tail, violet, or curved in various degrees (moon-seed, pink), or 

 coiled (hop), or rolled (spice-bush), or bent angularly (buckwheat), or 

 folded (Cruciferae). In the last case three modes are to be specially 

 noticed. 1, Incumbent, when the cotyledons fold over so as to bring 

 the back of one against the radicle (shepherd's purse) ; 2, accumbent, 

 when the edges touch the radicle (Arabis). 



