THE WILD ORCHID 



was scarcely reasonable to assume that insects 

 would persistently visit flowers where they re- 

 ceived no payment in return. Darwin examined 

 the flowers after sunshine, after rain, and at all 

 hours and under various conditions, but no nectar 

 could he find ; yet he observed that flies continually 

 visited the flowers and inserted their probosces 

 for considerable periods of time. Later he dis- 

 covered within the nectary tube a dehcate lining 

 membrane which could be penetrated very easil}^, 

 and which when punctured yielded copious juices. 

 Now this arrangement occupies the insect much 

 longer than if it had simply to insert its pro- 

 boscis and suck up the free nectar, and Darwin 

 suggests that this delay serves to insure that the 

 viscid pollen disk is securely attached before the 

 insect leaves the flower. 



So we might investigate a hundred other little 

 points of striking interest, such as the changing 

 of the position of the pollen masses ; or the fact 

 that the viscid base of the stamen remains sticky 

 while in the flower, but dries immediately on its 

 removal, attaching itself to the insect in such a 

 manner that it cannot be removed until it has 

 visited many flowers. It is impossible to shake 

 the pollen masses from a bristle or similar foreign 

 body after they are once attached ; the insect 

 therefore, has no alternative but to work them off 

 in the course of its travels. 



Finally, I may mention that the ovary or seed 

 vessel of each flower is t\vdsted. What is the 

 necessity for that curious feature ? It so happens 



141 



