122 CAUSE OF MOTION IN PLANTS. 



placed in order for this purpose. Such fine instruments are 

 required, that a surgeon's collection has scarce need of 

 more variety than the botanical dissecter. 

 Sensitive plant On immersing a specimen of the mimosa in a cylinder of 

 •oTmvcbox- water ' to see whether it produced much oxigen, I found 

 igeu, what I expected, that the oil in the plant would not permit 



the water to approach or touch it. It lay quite hollow from 

 the plant, which closed the moment I placed it there ; but 

 the next morning, when the sun shone full on it, it opened, 

 and remained thus till night, when it again closed. Again 

 the sun opened it, but from that time for near a fortnight it 

 remained open, and when 1 took it out of the water it had 

 lost all power of motion, and had I suppose dilated the 

 wire till no longer capable of stretching farther. It gave 

 not much oxigen. 



I should apologize for the extreme dryness of this letter ; 

 but to explain the formation of any sort of a machine can 

 only be done by the most simple and clear method, and 

 nothing is less entertaining than such a discourse. To ad- 

 vance a few steps nearer to truth is however a certain gain, 

 and if I have made out my proposition to the conviction of 

 those who study the subject, I am satisfied. Those who 

 possess a solar microscope I can only advise to follow me in 

 my experiments, for without seeing it, it is impossible to 

 conceive the amazing effect of light on plants, or almost to 

 imagine what are its powers. 

 Noperspira- ■"• w ^ no ^ ^ uls ^ this letter without adding a few words on 

 tion in plants, the perspiration of plants; a subject 1 have so repeatedly 

 brought forward. I mentioned in one of my last papers, 

 that, on placing a plant in a growing state, under a glass, I 

 put under the glass a paper doubled a few times so as to 

 raise the glass ■£$ of an inch from the stand ; to introduce 

 tinder the glass the smallest quantity of air possible; just 

 enough to prevent the air from stagnating, and the plant 

 from becoming sick or discomposed, and the plant gave out 

 no moisture. This gave me the idea, that it really was the 

 sickness of the plant, which caused the degree of moisture 

 Duhamel talks of, but which is certainly excessively exagge- 

 rated. But for a farther proof I enclosed a large plant in a 

 silver paper case, with a hoop very thin that would preserve 



it 



