22 



HT.IiUNGS. 



[sKf'TION 3. 



whole surface. It supplements the nutritive mutter contained in the 

 embryo. l>otli together form no large store, but sufficient for establishing 

 the seedling, with tiny root, stem, and pair of leaves for initiating its 

 independent growth; whieh in due time proceeds as in Fig. 41, 45. 



34. Smaller embryos, less developed in the seed, are more dcpendeui 

 upon the extraneous supply of food. The figures 46-53 illustrate fou 



grades in this respect. The smallest, that of the Peony, is still large enough 

 to be seen with a hand magnifying glass, and eveu. its cotyledons may be 

 discerned by the aid of a simple stage microscope. 



35. The broad cotyledons of j\lirabilis, or Four-o'clock (Fig. 52, 53), 

 with the slender cauliclc almost encircle and enclose the floury albumen, 

 instead of being enclosed iu it, as in the other illustrations. Evidently 

 here the germinating embryo is principally fed by one of the leaf-like coty- 

 ledons, the oilier being out of contact with the supply. In the embryo of 

 Abronia (Fig. 54, 55), a near relative of Mirabilis, there is a singular 

 modification; one cotyledon is almost wanting, being reduced to a rudi- 

 ment, leaving it for the other to do the work. This leads to the question 

 of the 



:'>i'i. Number of Cotyledons. In all the preceding illustrations, the 

 rmbryu, however diH'erent in shape and degree of development, is evidently 



Fio. 44. Seedling of .Moi-min; Glory more advanced (root cut away); cotyledons 



\\rll di'\.-ln].rd into foli.i'v l.'avrs: suivirding; intiTiiode and li-.-if well developed, 

 and tin- next forming. 45. Seedling more advanced; reduced to much below 

 n:itnr:il size. 



