MORPHOLOGY OF ANGIOSPERMS. 139 



Pollination and Fertilization. — Fertilization represents the 

 final stage in the work of the flower as a whole, and -has already 

 been defined as the union of the egg-cell and a male nucleus. 

 Pollination may be considered to include the transferral of the 

 pollen grains from the anther to the stigma and their subsequent 

 germination thereon, this latter process resulting in the produc- 

 tion of the male nuclei. Pollination thus represents but one series 

 of changes or processes which precede fertilization, for, while the 



Fig. 85. Diagrammatic representation of fertilization in an Angiosperm. d, floral 

 leaves: stamen consisting of filament (c) and anthers (a, b), one of which (b) has dehisced 

 exhibiting numerous pollen grains; e, nectar-secreting bodies; pistil consisting of ovary 

 (f), style (g) and stigma (h). On the latter pollen grains (i) are germinating, the tube (I) 

 of one having penetrated through the tissues of the stigma and style, entered the ovary, 

 passed along the wall, and entered the foramen (m), or opening of the ovule. The 

 ovule consists of that portion of the stalk which is united with the integuments and called 

 the raphe (n), outer integument (p), inner integument (q), chalaza (o), nucellus (s, s), 

 embryo-sac or megaspore (t) with egg-cell (z), synergids (v), antipodal cells (u), and the 

 nucleus in the center which gives rise to the endosperm. — After Sachs. 



pollen grain is going through the various stages in development 

 which lead to the formation of the male nuclei, a series of com- 

 plex changes are going on in the embryo-sac leading to the devel- 

 opment of the egg-cell (Fig. 85). 



