Francis E. Lloyd — 138 — Carnivorous Plants 



mucilage, and the cuticle remains intact. They might be delicate 

 flakes of cuticle exfohated from the remaining cuticle, but of this there 

 is no certainty. 



Movements of tentacles and leaf blade. — We must go back to 1782 

 to find the first record of studies of the modes of behavior of the ten- 

 tacles and leaf blade. These were carried on by the above mentioned 

 Dr. Roth, botanist as well as physician. He was stimulated to study 

 Drosera by reading Ellis' letter to Linnaeus in 1770 announcing the 

 discovery of Dionaea muscipula; and in his essay he makes cogent 

 comparisons between these two, the only then known carnivorous plants. 



According to Roth, if an ant be placed on a leaf, the glands re- 

 spond by bending, first the centrally placed, then, but much more 

 slowly, the glands most distant. Finally the leaf blade bends either 

 transversely, its apex approaching its base, or if the stimulus, say a 

 small fly, has been placed laterally, the side may bend over. The 

 rates of movement depend on external conditions, and are most rapid 

 in warm sultry weather. He remarks that D. longifolia reacts more 

 readily than D. rotundifolia, and that rain reduces sensitivity. 



The next contribution of major importance, by Nitschke, did not 

 appear till i860, eighty years later. Meanwhile, however, several bota- 

 nists had observed and discussed the matter. Somewhat previous to 

 1835 ^- P- °E Candolle had observed the response of the tentacles. 

 Treviranus (1838) quoted Roth (1782) but said that he failed to get 

 the results described by him. Hayne (date about this time, see 

 Nitschke i860) saw the response of the tentacles and that, at length, 

 the leaf blade bent and became spoon-shaped. In 1837 Meyen re- 

 viewed previous observations and while he could confirm the fact that 

 the tentacles as also the leaf blade were bent, he maintained the idea 

 that it was due not to irritability, but to the activity of a struggUng in- 

 sect pulhng over the tentacles toward itself. Milde (1852), however, 

 put this right by experiment. He placed small flies on the leaf, and ob- 

 served in 5 min. the outer tentacles bending inwards. Next day 

 the whole leaf was bent, and in 5 days again unrolled. A useful skep- 

 tic appeared in 1855 in the person of Trecul, who thought that the 

 insects were caught by young leaves which then retained their youth 

 position. Came then Nitschke (i860), who was the first to attack the 

 problem in a sustained way and with a critical attitude. His first 

 argument was directed against Trecul, and he established the general 

 correctness of Roth's observations. He believed that when a stimulus 

 has been applied at some point by the apphcation of an insect, the 

 surrounding tentacles bend their heads directly toward this point, 

 whether the position of the stimulating object is central or lateral. 

 The marginal tentacles move, he says, always in the "most direct" 

 path toward the point of stimulation. On this point the reader is re- 

 ferred to the work of Behre beyond. Nitschke regarded the behavior 

 as an expression of true irritability, and that Meyen's view that the 

 action of the tentacles is purely passive is wrong for a number of 

 reasons, especially cogent being the fact that young leaves do not se- 

 crete mucilage, and that neither they nor aged leaves are sensitive. 

 First when the leaves are widely open and rich in secretion is this the 

 case; even dead insects procure movements, if indeed somewhat less 



