18 DK. F. DARWIN ON THE 



in Pinguicula, Dioncea, Drosera, &c. Many observers have acceded 

 to my father's views on this subject ; but since he has given no 

 direct proof of advantage accruing to the plant from the cap- 

 ture and digestion of insects, a provisional acceptance of his 

 theory may fairly be followed by a request that such direct proof 

 should be furnished. It was to supply this want that an experi- 

 ment was set on foot several years ago by my father. Plants of 

 Drosera were cultivated in plates, each of which was divided into 

 halves by a strip of zinc plate. The plants on one side of the 

 partition were to have been fed, the other half being kept without 

 food, their growth &c. being compared. Unfortunately both the 

 fed and the starved plants died, either poisoned by the zinc, or 

 injured in some other way: in consequence of this accident the 

 experiment failed. 



The experiments here described are of precisely the same 

 nature as those begun by my father ; but profiting by his expe- 

 rience, I have used wooden instead of metal partitions. 



It may not be without interest to show, by reference to the 

 recent literature of the subject, that the want of some such expe- 

 riments has been rather widely felt. 



E. Morren, of Liege, although he considers* it beyond doubt 

 that the leaves can absorb animal matter from the captured 

 insects, remarks f that it ought to be experimentally established 

 that the absorption really contributes to the nourishment of the 

 plant. 



Cramer, of Zurich, goes carefully into the question J, and points 

 out (p. 33) that many experienced cultivators and naturalists, 

 such as Kurz, Munk, Eegel, Schenk, Veitch, and Williams, find 

 that Dion<ea§, Nepenthes, Sarracenia, CepJialotus, and Aldro- 

 vanda thrive as well when starved as when supplied with 

 insects. Cramer remarks that the question ought to be experi- 

 mentally decided. 



. * ■ La Digestion vegetale,' 1876. 



t * La Theorie des Plantes carnivores/ Liege, 1876. 



| ■ Insectfressenden Pflanzen,' 1876. 



§ I have found it a difficult task to starve -D/o??#a-plants properly. I have at 

 the present time 30 plants growing under a closely-gauzed case. 15 are being 

 starved, the others fed. On looking over the plants I have frequently found 

 woodlice caught by the starved leaves. I suppose they got in with the moss 

 used to pack the pots, or in some other way. An unpractised eye would easily 

 mistake a closed leaf containing a small insect for a young unopened leaf. 



