364 



HUTCHINSON'S POPULAR BOTANY 



will be observed that the hairs of plants have a great tendency to point 

 downwards, which, of course, constitutes them a more efficacious barrier " 

 (Lord Avebury). 



Lastly, in not a few cases creeping insects are kept away from the 

 interior of the flower by viscid secretions on the stem or calyx, to which 

 the unfortunate visitors get glued, and from which there is usually no 

 escape. Thus the calyx of Plumbago (fig. 442) is furnished with glandular 

 hairs, which stand out horizontally from the epidermis, and are fatal to 

 mairy a wandering aphis and small fly. The Honeysuckle (Lonicera) is 

 another familiar instance of a flower which produces these viscid protective 

 hairs on its calyx, but in the Catchflies (Silene nutans and S. noctiflora) they 

 are much more effective, as may be judged by the number of small insects 

 usually found glued to the calyx and flower-stalk. 



The Tutsan-leaved Dogsbane (Apocynum androsemifolium) is a plant 



__________________ which re- 



sorts to ex- 

 treme mea- 

 sures in 

 dealing with 

 un invited 

 guests. The 

 French call 

 it G o b e - 

 mouche, or 

 Fly-gulper, 

 and the 

 name is well 



bestowed. 



In f act, the 

 ~ 



stamens ot 



the flower have an ugly trick of nipping intruding flies by their probosces 

 and detaining them as captives till death puts an end to their miseries. 

 Then the filaments open and the dead insects are released. " Allured by 

 the honey on the nectary of the expanded blossom," says Knapp, in his 

 Journal of a Naturalist, " the instant the trunk [of the fly] is protruded to 

 feed on it, the filaments close, and, catching the fly by the extremity of 

 its proboscis, detain the poor victim writhing in protracted struggles till 

 released by death, a death apparently occasioned by exhaustion alone : the 

 filaments then relax, and the body falls to the ground. The plant will at 

 times be dusky from the numbers of imprisoned wretches." 



More than one plant is known in which the expulsion of unremunerative 

 visitors is effected, not by the plant itself, but by other and remunerative 

 insects. Kerner has enumerated four of such plants Gentaurea alpina, 

 G. ruthenica, Jurinea mollis, and Serratula lycopifolia, all of them belonging 



FIG. 446. GOATSBEARD (Tragopogon pratensis). 



The involucral bracts are longer than the ray-florets. 

 (" John-go-to-bed-at-noon "). but it 



The flower is supposed to close at noon 

 s seldom open so late. 



