PHANEROGAMIA. 391 



otherwise different from foliage leaves, and containing little 

 or no chlorophyll ; they are usually of some other color than 

 green, from the presence of soluble coloring-matters in their 

 cells. These modified parts, together with the organs more 

 immediately connected with the male and female reproduc- 

 tive cells, constitute what is known as the flower. 



499. The ovule, in its development, becomes surrounded 

 by one or two thin cellular coats, which grow from its base, 

 and almost completely enclose it, a little orifice only, the 

 micropyle, being left at its apex. In the lower Phanero- 

 gamia (the Gymnosperms) the ovule enclosed in its single 

 (rarely double) coat is otherwise naked, while in the higher 

 classes viz., the Monocotyledons and Dicotyledons it is en- 

 closed within the cavity of the ovary, a phyllome structure, 

 or, as it is commonly described, a modified leaf, which is 

 folded involutely so as to form a cavity. 



500. In the fertilization of the germ-cell there are no 

 spermatozoids developed ; instead of producing these, the 

 pollen grain develops a long slender tube, the pollen tube, 

 which penetrates the tissue of the ovule, and comes in con- 

 tact with the germ-cell in the embryo sac. The result of 

 fertilization is always the formation of a suspensor (some- 

 times called the pro-embryo) essentially like that in the 

 Selaginellw and Isoetece, and, at the lower end of this, an 

 embryo, consisting of a short stem, bearing generally one or 

 more rudimentary leaves (cotyledons) at one extremity, and 

 a rudimentary root at the other. The embryo grows at the 

 expense of the endosperm, upon which it gradually en- 

 croaches, and in many orders entirely displaces. While the 

 embryo is forming, the ovule becomes greatly enlarged, and 

 its outer coat generally much thickened and hardened ; it is 

 now called the seed, and soon separates at its base from the 

 parent plant. 



5O1. After a longer or shorter period of rest the seed 

 germinates, the root and stem elongate, and the former 

 pushes out through the micropyle ; in those seeds in which 

 much of the endosperm remains,* or in which the cotyle- 



* Seeds which contain endosperm are, in the ordinary descriptive 



