SPORES. | 59 
£ 
or, if two are present, one is minute or abortive. Such plants are also called 
ENDOGENS (¢vdoy, inside, z«vo24, to originate or grow), because their stems increase 
by internal accretions (197). Such are the grasses, the palms, the Liliacee, &c., 
whose leaves are mostly constructed with parallel veins. 
127. Dicotyledonous plants are such as bear seeds with two cotyledotia 
These are also called ExoGENS (¢&#, outside), because their stems increase by 
external accretions, including the bean tribe, 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 
network. 
FIG. 19. — Structure of seeds and germination; 1, seed of a garden bean; 2, the same 
after germination is commenced and the skin thrown off; 3, seed of Triglochin (magnified) ; 
a, fungous chalaza, }, raphe, c, hilum; 4, embryo ; a, cotyledon, }, radicle, c, fissure, beneath 
which lies the plumule; 5, vertical section of the same; d, the radicle seen beneath the 
fissure ; 6, germinating seed of Alisma ; a, cotyledon, b, plumule, c, radicle ; 7, seed of Canna 
lutea, vertical section, a, albumen, b, 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 Athiopica; a, seed, }, 
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, embryo of Pinus, showing the numerous cotyledons; 15, the same 
after germination has commenced; 16, embryo of Cuscuta, having no cotyledon. 
128. The pine and fir have seeds with from two to three cotyledons, while the 
dodder (Cuscuta) is almost the only example known of an embryo with no coty-_ 
ledon. 
129. A few plants, as the onion, orange, Conifers, &c., occasionally have two 
or even several embryos in a seed, while all the Cryprocamra, or flowerless 
plants, have no embryo at all, nor even seeds, but are reproduced from SPORES, 
(48) bodies analogous to the pollen grains of flowering plants. 
6 
