Francis E. Lloyd — 188 — Carnivorous Plants 



quired to procure reactions. They also found that the trap may be 

 stimulated to close by the apphcation of strong electrical stimuli to 

 the petiole. That various kinds of stimulating agents (cutting, hot 

 water at 65 deg. C, various chemicals, electrical stimuli) can effect 

 response has been abundantly shown by Darwin, Burdon-S Anderson, 

 MuNK, Macfarlane, Brown and Sharp. But it is easier to stim- 

 ulate by cutting, etc. the upper face of the leaf than the lower. If 

 the lower face is cut, it must be cut deeply so as to reach the upper 

 face tissues (Munk). Stimulation is not procurable by cutting the 

 outer marginal zone of the cilia (Munk). It appears therefore that 

 the more ventral tissues (Munk: the parenchyma) are sensitive, not 

 the more dorsal. But it remains the central fact that normally the 

 closure of the trap results from the stimulation of the sensitive hairs, 

 even though very slow closure may take place in response to applied 

 protein (chemonasty), after the power to react seismically has been lost. 

 It was natural for earlier observers, from Curtis on, to suppose the 

 whole of the hair to be sensitive, as did Darwin. "These filaments, 

 from their tips to their bases, are exquisitely sensitive to a momentary 

 touch" (1875). Sixteen years previously, however, Oudemans had 

 succeeded in showing experimentally that the sensitivity resides in 

 the basal region of the hair, to which Munk (1876) and Batalin 

 (1877) agreed. Darwin appears to have attached importance to the 

 flexible base in allowing the hair to bend rather than be broken by 

 the closing lobes. He saw that there is a constriction about the 

 base, merely mentioning it. Goebel (1891), in view of the config- 

 uration of the cells of the constriction (as well as of the organ in 

 general), believed that these receive, on movement of the "lever," 

 a "much stronger stimulus than any other leaf cell." The stimulus 

 is hindered from moving upward by suberized cells in the two courses 

 above (in which I find very little if any suberization). 



The cells of the constricted zone were regarded by Haberlandt 

 (1901) as special sense organs. The cells respond to compression, 

 but not to release from a constrained bent position (Brown and 

 Sharp), and if the hair is amputated, pressure on the remaining 

 base will procure closure (Brown and Sharp 19 10). 



The mechanism of closure. — The first effort to explain the mecha- 

 nism of closure in the trap of Dionaea was made by Meyen, in 1839. 

 To him the spiral vessels of the nerves, because of their spiral-spring- 

 like structure, seem to afford a suitable mechanism. If the idea is 

 naive, it still indicates the early desire and effort to answer the ques- 

 tion. 



Ziegenspeck much later (1925) {through von Guttenberg) at- 

 tributed importance to a hinge mechanism, saying that closure is 

 due to the loss of turgor by the cells of the tissues above the mid- 

 vein. Von Guttenberg (1925) showed this to be incorrect. 



Darwin described the closure of the trap as passing through two 

 phases. There is first a sudden response, bringing the edges of the 

 lobes into some approximation, enough at least to bring the ciHa in 

 position so as to make a sort of cage preventing the escape of suf- 

 ficiently large prey, and allowing small ones (ants especially) to escape 

 (Jones) (// — 6). This is followed by a slow movement during 



