246 



CRYPTOGAMS AND PHANEROGAMS. 



plant. After the spores are set free and germination has com- 

 menced, the spore-wall ruptures and the prothallium is exposed. 



The GYMNOSPERMSgo still further. The macrospore (embryo-sac) 

 germinates and forms internally a cellular tissue, designated in 

 former times by the name of albumen (endosperm), which is homo- 

 logous with the prothallium. It always remains enclosed in the 

 embryo-sac, and is aparenchymatous mass containing a large supply 

 of nourishment. In the upper part of the endosperm a number 

 of archegonia are developed which are in the main constructed in 



FIG. 251. Longitudinal sec- 

 tion of ovule of Abies cana- 

 densis. Inside the integumen< 

 (i) is seen the nucellns, n ; 

 m the micropyle. In the in- 

 terior of the nucellus is seen 

 an oval mass of cells, the en- 

 dosperm, and at its top two, 

 archegonia, c. The ovule is 

 turned in such a way that the 

 micropyle points upwards, 

 but usually it turns down- 

 ward in the Abietinea. 



FIG. 252. The ape : of the nacellus (n) of an ovule o 

 Abies: I long-shaped cells which guide the pollen-tube; 

 s the wall of the macrospore (embryo-sac) ; 7i the neck- 

 cells of the archegonium ; fc the ventral canal-cell; and 

 c the central cell (oosphere). The archegonia of the 

 Cryptogams should be compared with this (see pages 181, 

 208, 216). 



the same manner as those in the Cryptogams, but are still more 

 reduced, the neck consisting only of 4, 2, or 1 cell (Figs. 251, 252). 

 The ventral canal-cell is also formed, in the majority, as a small 

 portion cut off from the large central cell just beneath the neck ; 

 the larger remaining portion becomes the oosphere. When the 

 pollen-tube has passed down to the oosphere (Fig. 253) and fer- 

 tilisation has been effected, the oospore commences a cell-formation, 

 the final result of which is the formation of an embryo (the asexual 

 generation) which is provided with a thinner, lower end, termed 

 the suspensor. The embryo is forced more or less into the endo- 



