BOTANICAL GAZETTE. 



208 



148 

 172 



195 



2 12 

 272 

 318 



the substance upon the leaf was nearly dry and the marginal 

 tentacles exhibited a tendency to exi^and. 

 the marginal tentacles were nearly all reflexed; the other ten- 

 tacles were more or less reflexed. 



tentacles were all reflexed ; all that remained of the meat 

 was a dry scale which fell off when the leaf was touched, 

 there was no further change. 



the normal secretion had appeared on the tentacles.* 



*In the above experiment an exception seems to ai^pcisr to tlie rule that the 

 mar!i;in of the leaf bi'.coincs more or less ineurved accoi-ding to the substance 

 bein^ diirested; that substances easily- dii^ested excite the whole leaf and cause 

 •A much greater incurvation than those substances which are harder and require 

 more time for digestion and absorption. It seems to me that the following ex- 

 l)!anation is plausible. ^Aleat when placed upon a leaf seems to excite the 

 marginal and submarginal tentacles to greater activity, causing the glands to 

 pour forili a more copious supply of the viscid se(;retion. Thus may not the 

 power of the exciting force be" spent upon the exterior teutucks and their 

 glands causing a more gradual intlecliou of the tentacles and less excitement to 

 the leaf as a wliole ? 



I{<'ferring to the amount of secretion poured forth by the action of various 

 substances Darwin says: 



"It is a remarkable fact that when an ol)ject, such as a ])it of meat or an 

 insect, is placed on the disc of a leaf, as soon *as the surroimding tentacles be- 

 come considerably inflected, their glands pour forth an increased amount of se- 

 cretion. I ascertained this by selecting leaves^ with equal sized drops on the 

 two sides, and by placing bits of meat on one side of tlie disc; and as soon as 

 the tentacles on this side became much inflected, but befoie the glands touched 

 the meat, the drops of secretion became larger, ''i'his was rei)eatcdly (<b8erved, 

 but a record was kept of only thirteen ca-ses, in nine of which increa.sed secre- 

 tion was plainly observed; tlie four failures being due either to the leaves being 

 rather torpid, or to the bits of meat being too small to cause much inflection, 

 we nuLst therefore conclude that the central glands, when strongly exciieil, 

 transmit some influence to the glands of the circumferential tentacles, causing 

 them to secrete more copiously."— [Insectivorous Plants, p. 14.] 



The results of all my experiments indicate the truth of the above .statement 



of Dr. Darwin and further that mu.scular 

 fiber, insects and the like cause us- 

 ually a more copious supply of secretion 

 and less movement of the margin of 

 the leaf than egg-albumen. The latter al- 

 though exciting the glands somewhat, as 

 do all nutritious substances, causes more 

 marked incurvation of the margins, varj'- 

 ing in degree according to the vigor of the 

 leaf and the amount of substance placed 

 upon it. This will be shown in the tabu- 

 lated experiments of another series. 



The process of closing in the experi- 

 ment was so complete and typical that I 

 have caused it to be figured as illustrating 

 the position ofthe parts when closed (Fig.'^). 



The four tentacles that remain reflexed 

 show well the ])ositiou of the marginal 

 tentacles when there is no substance un- 

 dergoing digestion. The explanation of a 

 secondary experiment upon this leaf I re- 

 Fig. 2. (3X) serve for special consideration. 



