DIGESTIVE FLUIDS OF INSECTIVOROUS PLANTS. 377 



same manner, converting bodies of the kind mentioned into peptones. This digesting 

 secretion permeates then the body of the imprisoned animal and completely dissolves 

 it, so that at last, since the leaf again completely absorbs the secretion together with 

 the products of solution into itself, only the extremely fine chitinous envelope of the 

 animal remains behind. This I found to be the case virith several vigorous leaves 

 ■which spontaneously opened again in from four to six days after the seizure of large 

 wood-lice, and then continued living and healthy. The quantity of proteinaceous 

 substance which the leaves obtain in such cases is relatively very considerable, and 

 in my earlier researches I showed that just those plants which had occasionally 

 digested two or three wood-lice developed very vigorously, while the majority which 

 were prevented from seizing animals remained small and did not flower. If, on the 

 other hand, pieces of coagulated proteid scarcely as large as a wood-louse are 

 allowed to be digested by the leaves, the latter effect the process, it is true, but they 

 subsequently become discoloured and perish : only very small pieces of coagulated 

 proteid are digested without injury. The culture of these plants for years has 

 convinced me that they are able to develope into quite healthy, though small 

 specimens, without animal food, but that the digestion of animals invigorates them 

 considerably. Evidently it is here a matter of an addition of nitrogenous substance, 

 since the leaves are able to produce starch independently by means of their chlorophyll 

 contents, while the roots, few in number, evidently obtain but very little nitrogenous 

 substance from the cushions of Sphagnum in which they live; and the same appears to be 

 the case with all insectivorous plants. The digestion of small animals appears to be 

 not exactly an absolute necessity for their existence, but an aid to vigorous thriving. 



Our native species of Drosera, especially D. rolundifoh'a, found everywhere in 

 Sphagnum bogs, and occasionally in other places also, and which may be very easily 

 cultivated in windows if placed with the substratum in a flower-pot and watered with 

 pure water, belong to the same family as Dionea, but exhibit quite different adapta- 

 tions for the seizure of animals. The plant is small, and consists of a rosette of 

 8-10 leaves, from the midst of which a copiously flowering stem at length shoots up, 

 while only very few roots penetrate into the moss or turf. The leaves support, on 

 a petiole 2-5 cm. long, an almost circular lamina containing chlorophyll, the whole 

 area of which but rarely attains i sq. cm. At the margin of the lamina, as well as 

 on the whole of its upper surface, numerous so-called tentacles are situated ; these 

 are stalk-like outgrowths, each of which bears at its apex a gland of complicated 

 structure. The tentacles at the margin are the longest, those in the middle of the 

 lamina the shortest. In the non-irritated condition the tentacles are extended straight 

 outwards, and each glandular head is enveloped with a slimy secretion, forming a bril- 

 liant drop. If a small gnat, or fly, or other minute insect now comes in contact with the 

 slime of the tentacles, it remains hanging to it, and finally, after ineffectual struggles 

 to free itself, perishes. Here again the resulting phenomena can be called forth by 

 laying on the lamina a very small piece of hard proteid, flesh, or bread, some 1-2 mgr. 

 in weight; and here also the stimulus produces two effects — movements and chemi- 

 cal action. The movement consists in that the stalks of the tentacles in the course 

 of a few hours so curve at their basal portions that the glandular heads come to lie 

 exactly over the body of the insect ; whether the insect lies at the margin or in the 

 middle of the lamina of the leaf, the tentacles always curve in such a manner that 



