SEXUALITY OF PLANTS 



49 



way to the egg the male gametes are never exposed in 

 land-living Plants. Even in the pollen-grain the cell 

 that gives rise to them is protected by its usually 

 yellow, corky wall from too 

 intense sunlight, and from 

 risks of evaporation from its 

 surface. After the first stage 

 is passed, the transfer of the 

 gametes by the 'pollen-tube 

 is consistently within the 

 protecting tissues of the 

 carpel. Doubtless these pre- 

 cautions are very necessary 

 in Plants growing exposed 

 upon the land, which bear 

 their flowers containing the 

 gametes at the ends of their 

 branches. The protection 

 and nutrition afforded by 

 the parent is thus so well 

 secured that a large num- 

 ber of eggs is unnecessary. 

 Only one is present in each 

 ovule. But this is handled 

 physiologically with extreme 



Shepherd's Purse, the lower of Datura. J 

 Care. Each germ, Once estab- funiculus : m =micropyle : t =seed-coat : e - 



endosperm : c =cotyledons : pi =plumule : 

 Hshed by Syngamy, is CVl- *"=radicle. Enlarged. 



dently a thing of individual worth (Fig. 31). Yet 

 Tennyson, the poet of the Darwinian era, has done scant 

 justice to the value set on each germ. Impressed 

 with the ruthless waste of Organic Nature he cries : 



" How careful of the type she seems, 



How careless of the single life." 

 s.u. n 



FIG. 31. 

 Seeds in median section. The upper is of 



