I, ANIMALCULA OF INFUSIONS. 



23s 



tion regulates the fecretion. For this, a certain 

 heat is required j if too powerful, the quantity- 

 evacuated is no longer proportioned to the quan- 

 tity imbibed, which mufl be prepared in the vif. 

 cera. Excefs of tranfpiration debilitates the 

 plant, it infpiffates the fluids, dries and contrads 

 the veflels, and at length prevents circulation. 



The vegetables which perfpire httle fhould 

 undoubtedly fuifer moft in experiments fucli as 

 your's on feeds : fuch, for example, are ever- 

 greens. You know the celebrated Hailes has 

 proved that thefe trees perfpire much more than 

 others. Their fap feems more vifcous, therefore 

 has greater tendency to thicken and coagulate by 

 heat. 



In Jrficle 168, des Corps Orgam/es, I obferved 

 that we are yet ignorant of the power fecretly 

 governing the motions of the fap. It does not 

 refide in the leaves alone ; the bleeding of the 

 vine affords cogent evidence of it. Branches 

 which had been intentionally dried, and no long- 

 er would raife coloured liquors as other branches, 

 yet green, and without leaves, raifed it perfedly i 

 Thefe branches, I fay, fufliciently prove, that 

 ihe courfe of the fap depends on fome fecret mo- 

 tion of the veffels, which is deflroyed when they 

 are dried. But 2 1 2° or 232^ apparently are not 

 enough to tfiea complete deficcation of all vege* 

 tables ; fome expand in a certam meafure even at 

 this heat. Thefe curioiis experinient? certainly 



m?ri$ 



