PROTECTION BY THICKETS OF HAIES. 65 



In still more numerous species the access of ants 

 and other creeping insects is prevented by the presence 

 of spines or hairs, which constitute a veritable chevaux 

 defrise. Often these hairs are placed on the flowers 

 themselves, as in some verbenas and gentians. Some- 

 times the whole plant is more or less hairy, and it 

 will be observed that the hairs of plants have a great 

 tendency to point downwards, which of course con- 

 stitutes them a more efficacious barrier. 



In another class of cases access to the flowers is 

 prevented by viscid secretions. Everyone who has any 

 acquaintance with botany knows how many species 

 bear the specific name of ' Viscosa ' or ' Glutinosa.' 

 We have, for instance, Bartsia viscoaa, Robmia viscosa, 

 Linum viscoswm, Euphrasia viscosa, Silene viscoaa, 

 Dianthus viscidus, Senecio viscosus, Holosteum ghi- 

 tinosum, &c. Even those who have never opened a 

 botanical work must have noticed how many plants are 

 more or less sticky. Why is this ? What do the plants 

 gain by this peculiarity ? The answer probably is, at 

 any rate in most cases, that creeping insects are tlius 

 kept from the flowers. The viscid substance is found 

 most frequently and abundantly on the peduncles im- 

 mediately below the blossoms, or even on the blossoms 

 themselves. In Epimedium, aVpinum, for instance, 

 the leaves and lower parts of the stem are smooth, 

 while the peduncles are covered with glandular, viscid 

 hairs. The number of small insects which are limed 

 md perish on such plants is very considerable. Kemer 



