111.] THE FERTILISATION OF FLOWERS. 53 
the insect must alight on the labellum, and in push- 
ing its proboscis down the nectary, strikes its head 
against the pollinia, which, being sticky at their 
Fic. 66, 
bases, become attached to the insect’s head. Owing 
to the weight of the pollen and the slenderness of the 
stalks they gradually lose their erect position and 
Fic. 68. 
assume one more horizontal, so that on visiting 
another flower the pollinia strike exactly against the 
stigmas. In a foreign species (Catasetuim) certain 
