'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 GYMNOsi'ERMSgo still farther. 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 prothalUnm. It always remains enclosed in the 

 i-mhnjo-sac, and is a parenchymatous 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 



t - 



FIG. -51. Longitudinal sec- 

 tion of ovule of Abies cana- 

 iltnsif. Inside the integument 

 ( ; ) is seen the nucellus, n ; 

 in the micTopyle. In the in- 

 terior of the nucelliis is seen 

 :in oval mass of cells, the en- 

 tm, anrl at its top two 

 arche^oniii, c. The ovule ia 

 turned in such a way that the 

 micropjle points upwards, 

 but usually it turns down- 

 ward in the Abietinfce. 



FIG. 252. The apex of the nucellus () of an ovule of 

 Abies: I lonK-^haped cells which guide the pollen-tube; 

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

 cells of the arcbeponinm ; ); 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 oosphei-e (Fig. 253) and fer- 

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

 tin- linal 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 mor'e or less into the endo- 



