I 



Vk Bell on the Phyftotogy of Plants. 415 



of conrfe the ftem of the tree would have con- 

 traiSted itfclf into a fmaller compafs. * 

 . We are now to confider in what diredion the 

 fluids of plants are tranfmitted. 



I. Of the Courfe of the Succus Communis, or Sap. 



Botanifts have made many experiments to 

 afcertain the courfe of the fap. Early in the 

 fpring, when the fap begins to flow, incifions 

 have been made in the trunk and branches of 

 trees, as far as the pith -, and, in fuch cafes, it has 

 been conliantly found, that a larger quantity 

 of fap flowed from the fuperior, than from the 

 inferior margin of the incifion. This circum- 

 ftance led to the opinion, that in the beginning 

 of the fpring, great quantities of moifture are 

 abforbed by trees from the atmofphere, and 

 hence the fource of the abundance of fapt But 

 this conclufion, I found to difagree with the phe- 



* To determine this queftion abfolutely, it may feem, 

 that the moll certain and obvious method would be by in- 

 jedlions, the great fource of our icnowledge of the anatomy 

 of animals. They have been employed by Bonnet, Dr. 

 Hope, and others, but they have failed. They rife a con- 

 fiderable way into plants, but as, in different cafes, they 

 take different courfes, from this, and other circumftances, 

 there is reafon to believe, that their conrfe, and that of 

 the fap, are materially different from each other. J. C. 



t Duhamtl and others. See Phyf. des Arbres, Tom. I. 

 p. 67. 



nomena 



