VOL. XXIX.] I'HILOSOPHICAL TRANSACTIONS. 255 



animals, have diversities of food, a method of generating, and certain periods 

 of life. Of the amphibious race, vi^hich live as well on land as in the waters, 

 are the willows, rushes, mints, &c. these are not unlike in many respects to the 

 otter, tortoise, frog, &c. The aquatics, whether of lakes, rivers, or the sea, 

 are very numerous ; these may be compared with the fish-kind, and like them 

 will not live out of their proper element. In fresh waters are the water-lilies, 

 plantains, &c. and in the sea, corals, fuci, &c. Plants seem to possess only the 

 next degree of life below the most stupid animal ; or where animal life ceases, 

 there the vegetable life seems to begin. The seasons of motion in plants are 

 the same with those of animals, which sleep during the winter: an artificial 

 heat will give motion to either of these in the coldest season. 



The common opinions relating to the motion of the sap, are as follow : First, 

 the sap does not rise by the pith ; because some have observed the trunks of 

 large trees to be without that part, and yet the same trees have continued to 

 put forth fruit, and branches on their tops. I have observed, that the pith is 

 not found in those branches of a tree which exceed two or three years growth ; 

 and it is certain, that the pitli which is in a branch of this year, will (the 

 greatest part of it) be distributed into those boughs which form themselves the 

 next season. 



It is said by some, that the tree does not receive its nourishment by the bark, 

 for that trees having lost that part, will still continue their growth. Others 

 tell us, that if the bark be cut away round the trunk of a tree, it will presently 

 die. These various opinions seem to have been taken up without extraordinary 

 consideration, on the belief that a tree has only one bark : whereas, on exa- 

 mination with the microscope, we find 4 distinct coverings to each branch, with- 

 out the woody parts. The two outermost barks may be taken from a tree with- 

 out great damage, but the other two, which lie nearer the wood, being stripped 

 off, will kill the tree. 



Some affirm, that the sap neither rises nor falls in the woody part of a tree, 

 because they have not been able to perceive any sap to issue out of that part, 

 when a branch has been cut. The microscope plainly shows us the vessels in 

 the wood, through which the sap rises from the root ; but as these tubes are 

 not large enough to admit into them any thing more gross than vapour, so they 

 have not been esteemed to be of any great use. But the explanation of the 

 adjoined figure will in some measure discover their office, and that of such 

 other parts of a plant as are severally designed for the growth of vegetables : 

 but it will first be proper to inquire a little into the nature of the root. 



The root of a tree is chiefly composed of a parenchyma, more gross than that 

 in the stem or body of the tree ; it has also vessels and a covering. The root. 



