PHANEEOGAMIA 



435 



The female flowers resemble the male in general structure, 

 carpels are generally scale-like, outspread, 

 and never united ; they bear a varying 

 number of ovules, most frequently two 

 (Fig. 366). 



The embryo - sac enclosed in the 

 basal portion of the nucellus (Fig. 367, 

 nc) gives rise by a process of multicellular 

 formation, preceded by free nuclear divi- 

 sion, to a parietal cell-layer, and by the 

 increase of this layer to a female 

 prothallium, which completely fills the 

 embryo -sac (<?). Special cells of the 

 prothallium, situated at the apex of the 

 embryo-sac, then become converted into 



The 



i — m 



nc 



Fig. 366. — Pinus silvestris. fr, Fertile 

 scale with two ovules (s) ; m, pro- 

 longations of the integument of the 

 ovules; c, mucro ; b, cover-scale, 

 (x 7.) 



ARCHEGONIA. Each ARCHE- 



GONIUM consists, as in the 

 Pteridophytes, of a ventral 

 portion containing the egg- 

 cell, of a neck, in this case 

 composed of fewer cells, and 

 of a ventral canal-cell (Fig. 

 367). 



Fertilisation is effected 

 in the manner common to 

 all Phanerogams, by the 

 entrance into the arche- 

 gonium of a male cell from 

 the pollen-tube and its union 

 with the egg-cell (Fig. 368, 

 B, C). 



The nucleus of the em- 

 bryo, arising from the fusion 

 of the male and female 

 nuclei, twice undergoes bi- 



Fig. 367. — Median longitudinal section of an ovule of .... n - ,-t -, 



Picea vulgaris, ,, Embryo-sac filled with endo- partition, usually in the end 

 sperm ; a, archegonium showing ventral (o) and neck of the egg-Cell Opposite the 



p > neck of the archegonium, 

 and thus four cells are pro- 

 duced lying in the same 

 plane ; these by transverse divisions give rise to several tiers of cells. 



portion (c) ; n, nucleus of egg-cell ; nc, nucellus ; 

 pollen-grains ; f, pollen-tube ; i, integument ; s, seed- 

 wing. 



