| OCR Text |
Show 210 DROSERA ROTUNDIFOLIA. CHAP. IX. wished therefore to ascertain whether camphor would render the leaves ~f Droser~ more sensitive to mechanical irritation than they naturally are. Six leaves were left in distilled water for 5 m. or 6 m., and then gently brushed twice or thrice, whilst still under water with a soft camel-hair brush; but no movement ensued. Ni~e leaves, which had been immersed in the above solution of camphor for the times stated in the following table were next brushed only once with the same brush and in the ;arne manner as before; th~ results are given in the table. My first trials were made by brushing the leaves whilst still immersed in the solution; but it occurred to me that the viscid secretion round the glands would thus be removed, and the camphor might act more effectually on them. In all the followino· trials therefore, each leaf was taken out of the solu- o ' . tion, waved for about 15 s. in water) then placed 1n fresh water and brushed, so that the brushing would not allow the freer access of the camphor; but this treatment made no difference in the results. Ul Lengtl1 of QJ > Length of Time between ~ the Immersion C1> ~ Immersion in Length of Time between the Act of Brushing of the Leaves ln ...... tbe Solution 0 the Solution and the Inflection of the Tentacles. and the First h 1l of Camphor. Sign of the s::s Inflection of the z Tentaclf'S. -- --·--- 1 5m. {3m. considerable inflection ; 4 m. all} the tentacles except 3 or 4 inflected. Sm. 2 5m. 6 m. first sign 0f inflection. 11 m. 3 5m. { 6 mpl. a3i0n si.n fslleicgthiot nin. flection ; 7 m. 30 s.} 11m. 30 s. 4 4 m. 30 s. {2 m. 30 s. a trace of inflection; 3 m.} plain; 4 m. strongly marked. 7m. 5 4m. {2 m. 30 s. a trace of inflection ; 3 m.} plain inflection. 6 m. 30 s. 6 4m. {2m. 30 s. decided inflection; 3m. 30 s.} strongly marked. 6 m. 30 s. 7 4m. {2 m. 30 s. slight inflection; 3 m.} plain ; 4 m. well marked. 6 m. 30 s. 8 3m. {2m. trace of inflection; 3 m. con-} siderable, 6 m. strong inflection. 5m. 3 3m. { 2 m. trace of inflection ; 3 m. con-} siderable, 6 m. strong inflection. 5m. Other leaves were left in the solution without being brushed; one of these first showed a trace of inflection after 11 m.; a second after 12 m.; five were not inflected until 15 m. had CHAP. IX. E SENTIAL OIL , ETC. 211 elapsed, and two not until a few minutes later. On the other hand, it will be seen in the right-hand column of the table that most of the leaves subjected to the solution, and which were brushed, became inflected in a much shorter time. The movement of the tentacles of some of these leaves was so rapid that it couJd be plainly seen through a very weak lens. Two or three other experiments are worth giving. A large old leaf, after being immer ed for 10 m. in the solution, did not appear likely to be soon inflected; so I brushed it, and in 2 m. it began to move, and in 3 m. was completely shut. Another leaf, after an immersion of 15 m., showed no signs of inflection, so was brushed, and in 4 m. wn,s grandly inflected. A third leaf, after an immersion of 17 m., likewise showed no signs of inflection; it was then brushed, but did not move for l hr.; so that here was a failure. It was again brushed, and now in 9 m. a few tentacles became inflected; the failure therefore was not complete. We may conclude that a small dose of camphor in solution is a powerful ~timulant to Drosera. It not only soon excites the tentacles to bend, but apparently renders the glands sensitive to a, touch, which by itself does not cause any movement. Or it may be that a slight mechanical irritation npt enough to cause any inflection yet gives some tendency to movement, and thus reinforces the action of the cn,mphor. This latter view woulcl have appeared to me the more probable one, had it not been shown by M. Vogel that camphor is a stimulant in other wn,ys to various plants and seeds. Two plants bearing four or five leaves, and with their roots in a little cup of water, were exposed to the vapour of some bits of camphor (about as large as a filbert-nut), under a, vessel holding ten fluid ounces. After 10 hrs. no inflection ensued; but the glands appeared to be secreting more copiou ·ly. The leaves were in a narcotised condition, for on bits of meat being placed on two of them, there was no inflection in 3 hrs. 15 m., and even after 13 hrs. 15 m. only a few of the outer tentacles were slightly inflected; but this degree of movement shows that the leaves bad not been killed by an exposure during 10 hrs. to the vapour of camphor. Oil of Caraway.-vVater is said to dissolve about a thousandth part of its weight of this oil. A drop was added to an ounce of water and the bottle occasionally shaken during a day; but many minute globules remained undissolved. Five Jen,vc;s were immersed in this mixture; in from 4 m. to 5 m. there wafl some inflection, which became moderately pronounced in two or r 2 |
