72 



STRUCTURAL BOTANY. 



[60, 61. 



MONOCOTYLEDONS are plants bearing seeds with one 

 cotyledon ; or if two are present, one is minute or 

 abortive. Such plants are also called ENDOGENS, be- 

 cause their stems do not grow exogenously ( 421). 

 Such are the Grasses, the Palms and Lilies, whose 

 leaves are mostly constructed with parallel veins. 



216 



217 



214, Dicotyledonous (Bean). 215, Monocotyledonous (Wheat). 216, Polycotyledonous (Pine). 217, 

 Acotyledonous (zoospore of one of the Confervae). (r, r, r, radicle ; p, p, p, plumule ; c, c, c, cotyledon ; 

 a, albumen.) 



182. THE DICOTYLEDONS are plants bearing seeds 

 with two cotyledons. These are also called EXOGENS, 

 because their stems grow by external accretions ; in- 

 cluding 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 

 ( 280). More than two cotyledons are found in 

 the seeds of Pine and Fir ; while the Dodder is 

 almost the only known example of an embryo with no 

 cotyledon. 



183. The position of the embryo, whether with or 

 without albumen, is singularly varied and interesting 

 to study. It may be straight, as in Cat-tail and Vio- 

 let, or curved in various degrees (Moonseed and Pink), 

 or coiled (Hop), or rolled (Spicebush), or ~bent angularly 

 (Buckwheat), or folded (Cruciferae). In the last case 



