C4 DKOSERA ROTUNDIFOLIA. [Cuap. V. 



CHAPTER V. 



THE EFFECTS OF NON-NITROOENOUS AND NITROGENOUS ORGANIO 

 FLUIDS ON THE LEAVES. 



Non-nitrogenous fluids Solutions of gum arabic Sugar Starch Diluted 

 alcohol Olive oil Infusion and decot-tion of tt-a Nitrogenous fluids 

 Milk Urine Liquid albumen Infusion of raw meat Impurti 

 mucus Saliva Solution of isinglass DiUbrcncc in the action of 

 these two sets of fluids EKicoction of green peas Decoction and infu- 

 sion of cabbage Decoction of grass leaves. 



When, in 1860, I first observed Drosera, and was led to 

 believe that the leaves absorbed nutritious matter from in- 

 sects which they captured, it seemed to me a good plan to 

 make some preliminary trials with a few common fluids, 

 containing and not containing nitrogenous matter: and the 

 results are worth giving. 



In all the following cases a drop was allowed to fall from 

 the same pointed instrument on the centre of the leaf; and 

 by repeated trials one of these drops was ascertained to be 

 on an average very nearly half a minim, or f\^ of a fluid 

 ounce, or .0295 cc. But these measurements obviously do 

 not pretend to any strict accuracy; moreover, the drops of 

 the viscid fluids were plainly larger than those of water. 

 Only one leaf on the same plant was tried, and the plants 

 were collected from two distant localities. The experiments 

 were made during August and September. In judging of 

 the effects, one caution is necessary: if a drop of any ad- 

 hesive fluid is placed on an old or feeble leaf, the glands of 

 which have ceased to secrete copiously, the drop sometimes 

 dries up, especially if the plant is kept in a room, and some 

 of the central and submarginal tentacles are thus drawn to- 

 gether, giving to them the false appearance of having become 

 inflected. This sometimes occurs with water, as it is ren- 

 dered adhesive by mingling with the viscid secretion. Hence 

 the only safe criterion, and to this alone I have trusted, is 

 the bending inwards of the exterior tentacles, which have 

 not been touched by the fluid, or at most only at their bases. 



