50 Chapters in Modern Botany chap. 



from its leaves, but can actually thrive by their aid alone, 

 if supplied with a little nitrogenous material. Bennett 

 described, not only in Drosera, but also in Dionsea and 

 Nepenthes, what he termed "absorptive glands" lying 

 beneath the epidermis, and sometimes furnished with 

 papillae, which rise above the surface. 



Utility. — Relatively complete as Darwin's study of 

 Drosera and other insectivorous plants was, it did not 

 adequately meet the scepticism of those who doubted the 

 utility of the habit. Though Knight in 1 8 1 8 had thought 

 that plants of Dionasa which he fed with morsels of beef 

 throve better than others not so treated, many observers 

 have since failed to see any improvement on insectivorous 

 plants when regularly fed, or any disadvantage when 

 prevented from obtaining animal food altogether. And 

 others have gone so far as to assert that animal food was 

 hurtful, having injured or killed their plants by feeding. 



But it is obviously hazardous to draw conclusions as to 

 the utility of the insectivorous habit from plants under 

 cultivation. For it may be that plants living in the green- 

 house have a richer supply of nitrogenous food from their 

 roots than they can in natural conditions secure. Sundew 

 and butterwort very often grow among bog-moss on the 

 moors, hardly rooted, and therefore less adapted than 

 ordinary plants to absorb nitrogenous salts from their soil, 

 even supposing that these were present in abundance ; 

 which, it is worth noting, recent analyses of boggy soils 

 show they are not. Here indeed may be the grounds of a 

 fresh argument, since this relative scantiness of nitrogenous 

 supplies in the natural surroundings of insectivorous plants 

 may render them in part dependent on their peculiar animal 

 diet. 



Again, although it has often been noticed that a leaf of 

 sundew or fly-trap may suffer, or even die, from the effects 



