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

 ( ENDOGENS (fvJov, inside, yivofx-xt, to originate or grow), because their stems increase 

 by internal accretions (197). Such are the grasses, the palms, the Lihacese, &c., 

 whose leaves are mostly constmcted with parallel veins. 



127. Dicotyledonous plants^ are such as bear seeds with two cotyledons 

 These are also called exogexs (t%a>, outside), because their stems increase by 

 external accretions, including the bean ti-ibe, the melon tribe, all our forest trees) 

 &c. These are also distinguished at a glance,, by the structure of their leaves, 

 which are reticulate-veined, that is, with veins dividing and uniting again, like 

 netwoi'k. \ 



FIG. 19. — Slructure of seeds and germination ; 1, seed of a garden bean ; 2, tlie same 

 after germination is commenced and tlie skin thrown off; 3, seed of Triglochin (mag:nified) ; 

 a, fungons chalaza, 6, raphe, c, hilum ; 4, embryo ; a, cotyledon, 6, radicle, c, fissure, beneath 

 which lies the plumule ; 5, vertical section of the same ; rf, the radicle seen beneath the 

 fissure ; G, germinating seed of Alisma ; a, cotyledon, 6, plumule, c, radicle ; 7, seed of Canna 

 lutea, vertical section, a, albumen, 6, embryo ; 8, fruit of Mirabilis, showing the commence- 

 ment of germination, the embryo protruding the radicle; 9, the same, having thrown off the 

 pericarp and become a young plant; 10, germinating seed of Calla ^thiopica ; a, seed, 6, 

 first leaf of plumule, c, radicle ; 11, section of the fruit of a grass with the embryo at base; 

 12, the same after germination has commenced ; 13, the germination completed, and the 

 young plant formed; 14, embrj-o of Pinus, showing the numerous cotyledons; 15, the same 

 after germination has commenced ; IG, embryo of Cuscuta, having no cotyledon. 



128. The pine and fir have seeds with from two to throe cotyledons, while the 

 dodder ( Ciiscuta) is almost the only example known of an embryo with no coty- 

 ledon. 



129. A few plants, as the onion, orange, Conifera;, &c., occasionally have two 

 or even several embryos in a seed, while all the Cetptog^uiia, or flowerless 

 plants, have no embryo at all, nor even seeds, but are reproduced from spokes, 

 (48) bodies analogous to the pollen gi-ains of flowering plants. 



