.S15CT. II 



PHANEROGAMIA 



j05 



the base of the egg-cell, where they arrange themselves in one jilane and undergo 

 a further division. Cell walls are formed between the eight nuclei of this eight- 

 celled pro-embryo. The cells form two tiers, those of the upper tier being in open 

 communication with the cavity of the ovum. The four upper cells then undergo 

 another division {F) and this is followed by a similar division of the four lower 







y 



n 



II'^Hwa:-:-:;/ 



Fig. 463. — Ficea exrelsa (A-C). Pinus kiricio (D-1). A, Mature ovum witli its nucleus (ou) and tlie 

 ventral-canal-cell (c?) ; iJ, the male nucleus (sji) within the ovum ; C, fusion of the male and 

 female nuclei ; D, the four nuclei produced by division of tlie nucleus of the embryo have 

 passed to the lower end of the ovum and are there in process of further division (only two of 

 the nuclei are visible in the section) ; E, Ei between the eight nuclei, first transverse and then 

 longitudinal walls are formed — the four upper nuclei remain in connection with the upper pjart 

 of the fertilised ovum, the lower nuclei are enclosed in independent cells ; F, further division 

 of the nuclei of the upper series ; G, the cells of the lower tier have divided ; H, four tiers of 

 nuclei are present, those of the upper tier not being separated from the general cavity of the egg- 

 cell ; /, the elongation of the middle tier of four cells to form the suspensor (s)lias commenced. 

 (A-C X 55, after Miyake ; D-G x 200, after Kildahl ; 11, I y. 104, after Coulter and 

 Chamberlain.) 



cells ((?). The pro-embryo thus consists of four tiers, each containing four cells, 

 the cells of the upper tier being continuous with the remaining portion of the ovum. 

 In the further development of the three lower tiers the middle tier elongates to 

 form the suspensor {Is) pushing the terminal tier from which the embryo will 

 arise into the tissue of the prothaMium or endosperm ; the cells of the latter are 

 filled with nutritive reserve material. 



