VEGETATIVE REPRODUCTION. 



209 



cross-pollination.* To secure pollination, and especially 

 cross-pollination, the agency of wind or water or insects is 

 employed. To the peculiarities of these various agents, 

 flowers adapt themselves in character of pollen, color, nectar, 

 odor, form of parts, time of deveolpment of stamens and 

 stigma, etc. For an account of these see ^^f 383-394. 



296. The torus. — In the vicinity of the flower leaves the 

 internodes of the stem are rarely developed, so that the nodes 

 from which the flower leaves arise are close together. More- 



FiG. 175. Fig. 176. 



Fig. 175. — Flower of sweetbrier rose, halved ; showing um-shaped torus. Compare fig, 



go. Natural size. — After Bessey. 

 ¥\G. 176. — The inflorescence of a fig, halved lengthwise ; showing common torus on 



whose interior surface many flowers are formed. Two fig wasps are near the opening 



of the flower chamber, one outside, while the other has just crawled in among the 



flowers. Natural size. — After Kemer. 



over, the axis is usually enlarged, so as to give greater space 

 for the numerous leaves. This enlarged portion is called the 

 receptacle or torus. When the leaves are removed or fall 

 naturally the torus shows ordinarily a rounded or conical 

 surface, with close-set scars left by their bases (fig. 172). 



* Since fertilization of the egg is the ultimate object of pollination and 

 generally its final result, the terms close- or self-fertilization and cross- 

 fertilization were formerly used. The word pollination is preferable. 



