VOL. XXIV.J PHILOSOPHICAL TRANSACTIONS. 189 



it is that the bark of such wood cannot be stripped off longwise, but only 

 circularly. 



I have asserted formerly, (says Mr. L.) that in all countries where there is 

 any winter, so far as to put a stop to the growth of trees, at all times as long as 

 the growth lasts the bark grows thicker, and that the new bark protrudes that 

 which was made before further and further from the wood; insomuch that in 

 the bark of old trees, one may cut a finger's breadth in depth, before coming 

 at any thing like greenness or sap : and by considering those barks carefully, it 

 may be seen what part of the bark from time to time is deprived of its nourish- 

 ment, and consequently what part of it is quite dead. By these observations I 

 have discovered in a twig of a cherry-tree, of one year's growth, that the bark 

 consists of at least 6 thin membranes, whose exceedingly thin vessels or fibres 

 extended thernselves circularly about the wood, and were very closely united to 

 each other. Fig. 4, pi. 7, represents one of these membranes, separated from 

 the rest, as viewed by the microscope ; where it may be observed that the 

 vessels or canals do not run longwise, but circularly about the wood ; on which 

 account the vessels cannot long remain whole ; but must from time to time be 

 broken in pieces, 



I next turned my thoughts to the beach-wood, because the greatest part of 

 that wood is covered with a red bark, which sticks close to the wood, and 

 grows yearly thicker ; and on the outside of that bark there is produced a 

 whitish sort of bark several times in a year, which falls off from the wood as if 

 it was peeled ; but this only happens in beach-wood of an ordinary thickness ; 

 for in the thickest wood this peeling or scaly sort of bark is not produced, and 

 then the bark grows very thick ; but the most part of such bark is pushed away, 

 and remains as it were without nourishment; and in such there is no outer scaly 

 sort of bark produced. Fig. 5 represents a small particle of this wood, as it 

 was cut across ; in which the ascending vessels or canals, both great and small, 

 are easily seen, and between which run the horizontal vessels, which receive 

 their juices from the ascending ones. Here qvtsr represents a particle of the 

 bark, in which the horizontal vessels, as they lie in the wood, and are continued 

 on to the bark, and from whence the bark is produced, are shown by mnop, 

 of which N and o do not go quite throughout into the bark, by reason of some 

 hard matter contained in it, as shown at x. But the horizontal vessels, that 

 are represented by prs, and mgvt, go throughout the wood into the bark, so 

 far as to preserve the bark from mortifying. 



Now as the horizontal vessels are continued from the wood into the bark, so 

 there sprouted out from every side of those vessels exceedingly small canals, which 

 run circularly about the wood, and so for the most part produced the bark of 



