262 



STRUCTURE AND VITAL PROCESSES OF PLANTS 



their long tongues into the tlower-tube to obtain the nectar hidden 

 in its depth. While thus hovering in front of the tlower they 

 touch the anthers of the four stamens that protrud'. from the 



tiowers. The style of these 

 flowers is bent back in a 

 long downward arch. The 

 moth will then move on 

 to another flower which 

 may have opened the 

 previous night and now 

 has its stamens curled up 

 but the style straight, so 

 that the moth cannot help 

 touching and thus polli- 

 nating it with the pollen 

 of the flower from Avhich 

 it came. 



(e) We have found 

 another contrivance to 

 avoid self-pollination in 

 the Orchids (page 161), 

 where the pollen-masses 

 are in separate pouches, 

 and can only be removed 

 by a bee which carries them to another flower to pollinate it. 



As cross-pollination is advantageous to the ])lant, and as the 

 plant is unable to move, it requires some assistance to carry the 

 pollen from one flower to another. This is ol)tained from insects 

 or from the wind. 



Fig. 246. — Flowers of Clerodendron, 

 1. First position of stamens and style. 



2. Second position of the same. 



3. Motli visiting the flower of 



Clerodendron. 



2. Pollination by the Agency of Insects. 



{a) What the plants can ofi'er to their guests. - Tlie convey- 

 ance of tlie pollen from one flower to another is not done by 

 animals purposely or voluntarily. They pay the i)laiits visits 

 for their own sake only. lUit while obtaining some benefit from 

 the plants they, in their turn, unconsciously rend(u- them a very 



