258 BEES AND BEE-KEEPING. 



of a sugary, glutinous fluid, which causes the pollen 

 grains to adhere ; the pollen tubes, which seem to re- 

 ceive nutrition as they push forward, now penetrate, 

 with astonishing rapidity, and to surprising distances,* 

 either passing through the channel of the style (/*, B, 

 Fig. 49), or its loose conducting tissue (st, A), into 

 the cavity of the ovary, where, in the darkness, they 

 travel on, as though endued with intelligence, un- 

 erringly finding the apertures in the primine and 

 secundine (the micropyle), by which one enters and 

 applies its now swelling end to the extremity of the 

 embryo sac. The two upper cells of the egg appa- 

 ratus [h, C, Fig. 50) in some cases absorb the end 

 of the wall of the embryo sac ; but always — by 

 methods, subject to variations in different orders— the 

 pollen tube transfers its protoplasm and nucleus, 

 by the agency of these helper cells, to the embryonal 

 vesicle. Since every ovule needs a pollen tube to 

 fertilise it, the number of tubes requisite will depend 

 upon the number of ovules, but usually many more 

 are produced than can be utilised. In the buckwheat, 

 e.g. (A, Fig. 49), we find but one ovule in each 

 ovary, while in many plants, especially orchids, they 

 are multitudinous. At B (the ovary of the pansy), six 

 are represented, but many more actually exist ; and 

 here we notice how beautifully suited to the exi- 

 gencies of fertilisation is the turning of the ovule 

 by unequal lateral development. Had these six 

 ovules stood straightly up, like that of the buck- 

 wheat, their micropylar apertures would have been 

 placed in an exceedingly unfavourable position for 



* In the common crocus, the style is frequently several inches in length. 



