Francis E. Lloyd 



— 142 



Carnivorous Plants 



As little indeed may one thus argue as about the nutritional value 

 of food taken by man from the action of the salivary glands, adds 

 ScHMED. It seems proper to conclude that the reactions of the ten- 

 tacles are general rather than specific. The length of time they remain 

 inflected, however, seems, in the absence of injury (several times noted 

 by Darwin) to be generally correlated with their opportunity for ab- 

 sorption. 



Mechanism of tentacle movement. — Nitschke pointed out that al- 

 though the tentacles can bend, there are no special motile organs, such 

 as occur e.g. in Mimosa. What then is the nature of the bending 

 movements of the tentacle? Though Darwin obtained no hght on this 

 question, it was answered by Batalin (1877). He made spaced marks 

 on the sides of the tentacle, and found that after a movement was com- 

 pleted, the distances had increased. When the recovery is complete, 

 these distances are maintained, showing that the bending is a growth 

 phenomenon. This was shown true also of the leaf blade. H. D. 

 Hooker (191 6) investigated the matter more thoroughly. In making 



Fig. 3. — Drosera rotundifolia. — A, Side views of a tentacle in process_ of bending, 

 beginning with the bottom figure; B, same in process of unbending, beginning with the 

 top figure; C, Side views of the same tentacle before and at close of the reaction (after 

 Hooker). 



his measurements of the tentacles during bending he made use of 

 natural marks supplied by the minute sessile glands to be found on the 

 surface of the tentacle stalk. By means of these measurements and of 

 camera lucida drawings, he got a detailed record of changes in dimen- 

 sions during bending and recovery. A set of his drawings are here re- 

 produced (Text fig. 3). Hooker found, as did Batalin, that the 

 movement, whether bending or unbending, is a growth phenomenon. 

 During bending acceleration of growth begins near the base along the 

 back (the convex surface) of the tentacle, and moves upward during the 

 bending phase, so that the tentacle end moves through an^ angle 

 of 215 to 270 degrees, beginning the movement within 1.5 minutes, 

 completing it in a few hours, or sometimes in as short a time as 17 

 min. 30 sec. (Darwin). The unbending movement results from in- 

 creased growth on the now concave side, and takes place at once if the 

 stimulus was a brief one, or is delayed as when the tentacles have 

 closed over prey. Here also growth begins near the base and moves 

 upward toward the gland. During neither phase is the growth neces- 



