Hair-like Trichomes. 79 



come in contact first with the stigma and then with 

 the anthers, and so will convey pollen from one flower 

 to another, and promote intercrossing. They will never 

 thrust their tender proboscis through the lateral chinks 

 between the adjoining scales, defended as these are by 

 pricklets. So far, therefore, the pricklets act as " path- 

 pointers" to invited guests. But inasmuch as they 

 also shut out all such smaller insects with shorter pro- 

 boscis, as would, in their absence, get at the nectar 

 without first striking the stigma and then getting 

 powdered with pollen, they are to be considered not 

 only as path-pointers, but also as protective appliances 

 against tinbidden guests. 



5. Access to Flowers impeded by Hairy Formations. 



The protective appliances hitherto considered are 

 developed as a rule along the road which creeping 

 insects must follow in order to pass from the ground to 

 the flowers, and only in exceptional cases are to be 

 found inside the flowers themselves. Viscid substances 

 indeed, collections of water, or chevaux-de-frise of sharp 

 prickles, could scarcely be placed with profit inside the 

 flower ; for this would prevent the visits of almost all 

 flying insects to the nectar. But amongst these flying 

 insects are, as is well known, not a few whose visits 

 are not merely advantageous but actually indispensable 

 for the production of germinable seeds ; and these, of 



