158 CARNIVOROUS PLANTS WITH ADHESIVE APPARATUS. 
aliment from prey were injurious to Dionwa, the plant would certainly have died 
out long ago. If, therefore, cultivated specimens of Dionwa have suffered from 
being fed with meat, fibrin, cheese, and other such materials, only this much is 
proved, that the nutriment in question was not beneficial to them owing to its 
quality or to its being too concentrated. 
As regards the other point, that Dionwa thrives well under cultivation, even 
when all visits from insects are excluded, we must, on the other hand, bear in mind 
that the successful growth of Dionea, like that of Drosera, Pinguicula, &e., is not 
conceivable unless in some way or another the nitrogen indispensable for the 
construction of the protoplasm is conveyed to the individuals in question. The 
source from which it is taken varies according to the site. If the roots are buried 
in deep sods of bog-moss upon a flat expanse of moorland, the supply of nitrogen 
from the ground, and also from the air, will be extremely limited, and probably 
insufficient; under these circumstances the nutriment derived from the dead bodies 
of captured insects would be not only useful and beneficial, but may be even 
essential. If, on the contrary, the place where the plants have been reared or have 
grown up spontaneously is such that they can obtain the requisite nitrogen from 
the ground or air, they are able without harm to dispense with the available source 
of nitrogen afforded by the capture of insects. It is worthy of notice that insect- 
ivorous plants always grow wild only in places that are poorly supplied with nitro- 
genous food. The majority occur in pools fed by subterranean water, whose course 
lies through layers of peat, or in the spongy peat itself, or in the sods of Sphagnwm. 
Others are rooted in deep chinks in the stone on the declivities of rocky mountains, 
whilst yet others occur in the sand of steppes. The water available in such situa- 
tions for absorption by the suction-cells is, to say the least, very poorly furnished 
with nitrogenous compounds; and the quantity of these compounds passing from 
the ground into the air at the places mentioned is extremely minute and inconstant. 
Under these circumstances, the acquirement of nitrogen from the albuminoid 
compounds of dead animals is certainly of benefit, and all the various pitfalls, 
traps, and limed twigs are explained as contrivances by means of which this 
advantage is secured. 
