INSECTIVOROUS PLANTS. 53 



When it is considered where the plant grows generally on ex- 

 tremely poor, peaty soil it is evident that the supply of nitrogen 

 would be quite deficient unless the plant had the power of obtaining 

 this important element from captured insects, and w^e can thus under- 

 stand how its roots are so poorly developed. These usually consist 

 of only two or three slightly divided branches from half to one inch 

 in length, furnished with absorbent hairs : it appears that they serve 

 only to imbibe water, though, of course, they will absorb nitrogenous 

 matter when supplied. 



Confirmation of these statements is furnished by some experi- 

 ments, concluded since the publication of Mr. Darwin's book, by Mr. 

 Lawson Tait, an account of which he sends to Nature, July 29, 18'75, 

 p. 251. Only the results can be stated, and those briefly : "It is cer- 

 tain that the sundew not only absorbs nutriment by its leaves, but 

 that it can actually live and thrive by their aid alone (that is, without 

 the aid of roots) ; that nitrogenous matter is more readily absorbed 

 by the leaves than by the roots, for over-feeding kills the plant sooner 

 by the leaves alone than by the roots alone." 



Mr. Tait also announces that from the secretion of Drosera dichio- 

 toma he has been able to separate a substance closely resembling 

 pepsin. 



If a tentacle receives an impulse fi*om its own glands the move- 

 ment is always toward the centre of the leaf (Fig. 5). 



FiQ. 5. Drosera rotundifolia. Diagram showing one of the exterior tentacles closely in- 

 flected ; the two adjoining ones in their ordinary pcaiiion. 



On the other hand, when the motor impulse comes from one side 

 of the disk, the surrounding tentacles, including the shoi't central 

 ones, all bend with precision toward the point of excitement, wherever 

 this may be seated. This is in every way a remarkable phenomenon ; 

 for the leaf falsely appears as if endowed with the senses of an ani- 

 mal {see Fig. 4). 



In every case the impulse from a gland has to travel for at least 

 a short distance to the basal part of the tentacle, the gland being car- 

 ried solely by the inflection of the lower part. When the central 



