Br. Bell on the Phyfiology of Plants. 423 



the rifing of the fap, when warmth is applied to 

 the leaves, but cannot account for its defcending 

 in the fame circunnftances, that is, when the at- 

 mofphere is warnner than the earth. But this 

 takes place conftantly, with rcfpedt to zhe fuccus 

 proprius, and it is probable, that part of the fap 

 has the fame courfe, both in the day and night. 

 2. The exertions of many plants, on the ap- 

 plication of ftimuli, afford another argument in 

 fupport of their mufcular power, and the fpon- 

 taneous motions of other plants confirm the 

 fame opinion. 3. Light admitted to plants, in- 

 creafes their perfpiration, and caufes a leaf, be- 

 fore inverted, to refume its natural pofition, * 

 The influence of darknefs contrafts thefe effe(5ts, 

 and it produces, what is called, deep in plants, 

 although the heat of the atmofphere be not 

 diminifhed. Thefe fadls feem to prove the 

 irritability, or mufcular power of vegetables; 

 4. If the fluids of plants are conveyed through 

 veflels, as I have already rendered it probable 

 they are, can we fuppofe thefe tubes to be of fo 

 fmall a diameter, as, by capillary attraflion alone, 

 to raife the juices from the roots to the fummits 

 of the loftiell trees ? 5. On the fuppoficion qf 

 the fluids being moved entirely by capillary 



* Mil/er in the Philofophical Tranfailions, and Bonnet, 

 §>ir 1' ufage des feuilles. 



E e 4. attraction. 



