Chap. 2.] Vajcidar Syftem of Vegetables. 13 



that, on ib interefting a fubject, no conclufloh can be 

 formed from the actual di flection of vegetables. It 

 however feems moil probable, that all the fluids of 

 plants are tranfmitted through vefiels, for the following 

 reafons. i. The exiftence of "oaja propria and vafa 

 fi&ria is difcoverable by the naked eye, and made ftill 

 more manifeft by the niicrofcope. That fuccus pro- 

 prim and air are contained in thefe is evident, and 

 therefore analogy leads us to believe, that the fuccus 

 ccmmunis is alfo contained in veflels. 2. Secretion, 

 of which vegetables have undoubtedly the power, is in 

 no inftance, that we know of, performed without 

 the action of veflels. 3. An experiment, made by 

 Dr. Haks, feems clearly to prove, that the fap is 

 contained within its own veflels, and does not fortui- 

 toufly pervade every interface of the plant. Fie 

 fixed an inftrument round the ftem of a vine, by 

 which its contractions and expanfions could be accu- 

 rately 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 detect a va- 

 riation of the hundredth part of a finger's breadth. 

 If the fap had been trarjfmitted, without veflels, 

 through the cellular fubftance, this, on the withdrawing 

 of the fap, would have been comprefled, and of courfe 

 the ftem of the tree would have contracted itfelf into 

 JL fmaller compafs *. 



* To determine this queflion abfolutely, it may feem, that the 

 moft certain and obvious method would be by injections, the 

 great fource of our knowledge of the anatomy of animals. They 

 have been employed by Bonnet,. Dr. Hope, and others, but the/; 

 have failed. They rife a confiderable way into plants, but as, in 

 different cafes> they take different courfes, from this and other 

 circumftances there is reafon to believe, that their courfe, and that 

 of the fap, are materially different from each other. 



' Botanifts 



