755 



the acid placed on two leaflets of a healthy plant gradually causes 

 contraction of the other leaflets, pair by pair. Solutions of opium 

 and corrosive poisons have no effect when applied this way. After 

 some time they dilate, but are insensible to external irritation : the 

 sensibility returns in about half an hour; but the leaflets appear as 

 if benumbed. 



" The plant exposed to the vapour of prussic acid is afliected in 

 the same way : ammonia appears to favour tiie recovery of the plant. 



"A cup containing dilute prussic acid was so placed that one or 

 two leaves, or sometimes a branch, of a healthy plant could be plung- 

 ed into the liquid, or left to repose on its surface. The leaflets re- 

 mained fresh and extended, but were almost immediately insensible. 

 Being left in this state for two hours, they were expanded ; and no 

 irritation could cause their contraction, though otherwise there was 

 no appearance of an unnatural state. At five o'clock in the evening 

 the leaves were left to themselves. At nine o'clock they were open 

 and insensible. At midnight they were still open, whilst all the rest 

 of the plant, and the neighbouring plants were depressed, contracted, 

 and in the state of sleep. On the morrow they resumed a little sen- 

 sibility, but seemed benumbed. 



" In the same manner M. Macaire has interfered with other plants 

 as to the state of sleep, and observes that prussic acid thoroughly de- 

 ranges the botanical indications of time of Linnasus." — Lindle.y's 

 Introduction, 294. 



MICKOSCOPICAL SOCIETY. 



October lith, 1846. — J. S. Bowerbank, Esq., F.R.S., President, 

 in the chair. 



A paper by John Anthony, Esq., on a method of rendering the 

 appearances in delicate structures visible by means of oblique trans- 

 mitted light. This method depends upon the placing the object in 

 such a position that the fine lines or other delicate markings are ex- 

 actly at right angles to the illuminating rays, when these lines, &c., 

 will be at their maximum of distinctness, and thus tissues may be 

 rendered distinctly visible whose existence, when viewed in the or- 

 dinary manner, might be considered as exceedingly doubtful. The 

 object employed to illustrate this position was the Navicula of the 

 Humber, one of the most delicate of test-objects, which, under ordi- 

 nary circumstances, appears perfectly transparent, but when viewed 



