PITCHER-PLANTS. 119 



received special attention since the subject of 

 carnivorous plants has been fairly under investiga- 

 tion. " The different manner," he says, " in which 

 vegetables exert their organic powers to effect the 

 destruction of insects is not, perhaps, unworthy of a 

 brief notice : some accomplish it by means of elastic 

 or irritable actions, adhesive substances, and so forth ; 

 but we have another plant in our green-houses, the 

 glaucous birthwort (Aristolochia glauca), that effects 

 these purposes without any of these means, but 

 principally by conformation. The whole internal 

 surface of the tubular flower is beset with minute 

 strong spines, pointing downwards ; these present no 

 impediment to the descent of the animal which may 

 seek for the sweet liquor lodged upon the nectary at 

 the base of the blossom, nor is there any obstruction 

 provided for its return by means of valves or con- 

 tractions, the tube remaining open ; but the creature 

 cannot crawl up by reason of the inverted spines; 

 and, to prevent its escape by flying up the tube, the 

 flower makes an extraordinary curve, bending up 

 like a horn, so that any winged creature must be 

 beaten back by striking against the roof of this neck 

 as often as it attempts to mount, and, falling back to 

 the bulbous prison at the base of the flower, dies by 

 confinement and starvation, and there we find it: 

 a certain number of these perishing, the blossom fades 

 and drops off." 



