246 



GROWTH OF TKEES. 



know not any thing more difficult to discover, or that has cost 

 me so much trouble to gain ; as it requires so perfect a know- 

 ledge of the formation of the tree, and the general disposition 

 of the several parts in each different wood : — but the dissecting 

 and comparing the shoots of autumn and spring, by fresh vege- 

 table cuttings, and watching in trees their increase, has at last 

 enabled me to effect it j audit will be much raore easy for a 

 person to follow me, now the matter is known, than first to 

 make the discovery. Choose a tree of any kind that you can 

 cut to pieces, take off a large branch near the stem at the be- 

 ginning of August ; between the wood and bark a row of al- 

 burnum will be found — it is distinguished by being of a clearer 

 and softer substance than any other in the tree : it is this albur- 

 Yearly in- ^^^m whiqli is deposited each season, half a circle at a time, 

 crease of sap. and which the next season becomes wood. You will then find 

 the bark and rind are retired back at the south side of the tree, 

 leaving a diminutive space between the alburnum and bark, 

 which is preparing for the season's increase. It is this 

 which causes them to be so easily severed, and makes this the 

 proper season for barking. Take a vegetable cutting of the 

 branch, and examine the alburnum in the solar microscope j 

 it will appear perfectly clear and free from all vessels, and to be 

 merely what I before announced it, a jelly of sap. Continue 

 to cat fresh specimens, and display them daily before good mag- 

 nifiers, and they will soon show the sap-vessels beginning to 

 run through this stripe of alburnum, and the bastard vessels 

 shooting also across it, but in a contrary direction. In a fort- 

 night's time, that part which was alburnum is now become per- 

 fect wood, and the jelly of sap will appear to be forming 

 beyond it, filling up that place from which the bark had re- 

 ceded for the purpose, and forming a new circle of alburnum, 

 which the next autumn, in its turn, will be converted into com- 

 plete wood. This must at once show how the wood and bark 

 are protruded in trees ; and end that eternal dispute, whether 

 the bark make the wood, or the wood the bark. It is certain, 

 that they are of a totally diirerent nature, and yet in one re- 

 spect agree in their formation. That it is the juices which 

 form the softer part of each ; that these coagulate, and then 

 wait for the growth of the separate vessels, which shoot out 

 vessel within vessel, thus lengthening as necessary, and pro- 

 truding 



