400 PHILOSOPHICAL TRANSACTIONS. |^ANNO 1773. 



that he does not believe it true, he determines nothing about it. The friends of 

 the circulation in plants have never been able to find in them any thing analogous 

 to that powerful organ, which is the promoter of it in animals, for want of such 

 an organ, they were forced to imagine valves and paps in the lymphatic vessels of 

 plants, by means of which the liquors once introduced into the sap vessels were 

 supposed to be hindered from going back ; but unfoilunately no body has ever 

 been able to discover these valves and paps, so diftiirent from the simple con- 

 trivances, by which nature is used to arrive at her ends. 



An experiment, which Mr. M. made, and of which he proposes giving an 

 account in this paper, throws a great light on this question, as well as on 

 several others; and the conclusions deducible from it appear to him decisive. 

 On the 12th of January, he placed several shrubs in pots against the windows of 

 his hot-house, some within the house, and others without it. Through holes 

 made for this purpose in the panes of glass, he passed a branch of each of the 

 shrubs, so that those on the inside had a branch without, and those on the out- 

 side one within ; after this, he took care that the holes should be exactly closed 

 and luted. This inverse experiment, he thought, if followed closely, could not 

 fail affording sufficient points of comparison, to trace out the difterences, by the 

 observation of the effects. 



The 20th of January, a week after this disposition, all the branches that were 

 in the hot-house began to disclose their buds. In the beginning of February, 

 there appeared leaves, and towards the end of it shoots of a considerable length, 

 which presented the young flowers. A dwarf apple-tree and several rose-trees, 

 being submitted to the same experiment, showed the same appearance then, as 

 they commonly put on in May; in short, all the branches which were within 

 the hot-house, and consequently kept in the warm air, were green at the end of 

 February, and had their shoots in great forwardness. Very different were those 

 parts of the same tree, which were without, and exposed to the cold. None of 

 these gave the least sign of vegetation ; and the frost, which was intense at that 

 time, broke a rose-pot placed on the outside, and killed some of the branches of 

 that very tree, which on the inside was every day putting forth more and more 

 shoots, leaves, and buds, so that it was in full vegetation on one side, while 

 frozen on the other. 



The continuance of the frost occasioned no change in any of the internal 

 branches. They all continued in a very brisk and verdant state, as if they did 

 not belong to the tree, which, on the outside, appeared in a state of the greatest 

 suffering. On the 15th of March, notwithstanding the severity of the season, 

 all was in full bloom. The apple tree had its root, its stem, and part of its 

 branches, in the hot-house. These branches were covered with leaves and 

 flowers; but the branches of the same tree, which were carried to the outside. 



