FERTILISATION. 



253 



botanically, the fruit ; here, at length, we have the 

 seeds, which are the ripened ovules, while the seed 

 vessel is the ripened ovary. But the change from 

 ovule into seed is not merely one of growth; it 

 depends upon the formation within the ovule of the 



es- 



mmM$ 



Fig. 49.— Ovaries, Ovules, Pollen Grains, and Tubes. 



A, Section through Ovary of Buckwheat (Polygonum fagopyrum)—s, Stigmatie 

 Surface; pg, Pollen Grains ; st, Style ; pt, Pollen Tube ; ov, Ovule ; s, Secun- 

 dine ; p, Primine ; n, Nucellus ; es, Embryo Sac; emv, Embryonal Vesicle. 

 B, Section of Pistil of Pansy (Viola tricolor)— s, Stigma; I, Lip; pt, Pollen 

 Tube ; ov, Ovules. C, Pollen Grains Various, Emitting Tubes— s, Portion of 

 Papillose Stigma. D, Ovule at a very Early Stage— n, Nucellus ; es, Embryo 

 Sac forming ; p, ditto Primine ; s, ditto Secundine. E, Developed Anatropous 

 Ovule of Viola tricolor ; Arrow indicating the Micropyle. F, Section through 

 same, more enlarged— es, P2mbryo Sac ; emv, Embryonal Vesicle ; pt, Pollen 

 Tube ; s, Secundine ; p, Primine ; n, Nucellus. 



embryo, which is itself the outcome of the definite 



process of fertilisation, now to be examined in detail. 



Taking a blossom of buckwheat, well-known as an 



