414 ^^' B^^^ °^ ^^^^ Phyfiology of Pknfs, 



intererting a fubje^t, no conclufion can be 

 formed from the a£tual difledlion of vegetables. 

 To me it feems moft probable, that all the 

 fluids of plants are tranfmitted through veflels, 

 for the following reafons. i. The exiftcnce of 

 vafa propria, and va/a aeria, is difcoverable by 

 the naked eye, and made fhill more manifeft 

 by the microfcope. That Juccus proprius and 

 air are contained in thefe is evident, and there- 

 fore analogy leads us to believe, that the Juccus 

 communis is alfo contained in veflels. 2. Secre- 

 tion, of which vegetables have undoubtedly 

 the power, is in no inftance, that we know of, 

 performed without the a6lion of veflcls. 3. An 

 experiment, made by Dr. HaleSy fecms clearly 

 to prove, that the fap is contained within its 

 own veflels, and does not fortuitoufly pervade 

 every interftice of the plant. He fixed an 

 inftrument round the (lem of a vine, by which 

 its contraflions and expanfions could be ac- 

 curately meafured ; but he found no difference 

 in the circumference of the trunk, when the 

 tree was full of fap, and when it was entirely 

 without it, although the inftrument employed 

 was fo nice, as to dete6l a variation of the hun- 

 dredth part of a finger's breadth. If the fap 

 had been tranfmitted, without vcffels, through 

 the cellular fubdance, this, on the withdrawing 

 of the lap, would have been comprefTed, and 



of 



