JtO j4fcenf of the Sap in Trees. — Geniwiaihn. 



fure of the winds. The females, which have a very long 

 fialk, turned into a fpiral like a fpiral fpring, rife at the fame 

 time to Jhe furfiice of the water by the expanfion of their 

 fialk; agitate themfelvcs around the male flowers, which ap- 

 proach them ; and when the rays of the fun begin to heat 

 the horizon, the ftalk falls back, and carries with it, below 

 the water, the female flowers, which then fliut. But in the 

 evening, as foon as the fun finks below the horizon, they re- 

 appear on the furface of the water. This is repeated feveral 

 times, but the author has not determined the number. In 

 the laft place, when the fecundation is etTefted, the flalk falls 

 hack entirely, and carries with it, to the bottom of the water, 

 the flower and the germ. 



Coulomb having caufed to be cut down, towards the end 

 of April, fome Italian poplars Covered with flowers, obferved 

 that one of them, which had been cut at the di fiance of fome 

 lines from the axis of the tree, emitted at the cut a noife like 

 that produced by the air when it iflues in abundance, and in 

 fmall bubbles, from the furface of a fluid, and that a great 

 tk-al of fap flowed from it. This experiment, being repeated 

 feveral times, was always attended with the fame fuccefs; 

 from which he concludes, that the fap in large trees does not 

 afcend in a fenfible manner, but towards the axis, which 

 forms the medullary canal. To afccrtain this facl, he caufed 

 feveral of thcfe trees to be pierced with a gimblet; but the 

 inftvument was fcarcely moiflened till it had arrived within 

 two or three centimetres of the centre of the tree : when it 

 approached the centre, fap iffiied in abundance, with a con- 

 tinued noife of air-bubbles, which afcended with the fap, and 

 buril in the orifice formed by the gimblet. 



SauflTure the fon has publiflied refcarches on the influence 

 wiiichoxygen eas has on the germination of plants. The greater 

 part of naturalids, fiys he, who have examined the iofluence 

 of atmofpheric air on gerniination, have perceived, that when 

 feeds are placed in contact with water and pure azotic gai 

 they do not germinate ; and that there is a production of 

 carbonic acid, which, mixing itfelf with the azotic gas, in- 

 creafes the volume of the atmofphere of the plant. They have 

 liien that, when oxygen gas is fubftituted in the preceding 



experiment 



