Qtf THE STEM OF TREES, 233 



perhaps be accused of presumption, in venturing to in* 

 trodtsce so many new ideas; and depending thus on mi/self 

 only; but I recount merely what I have seen in a. -very 

 good solar microscope ; if my deductions are false, I detail 

 my reasons ; and every reader may judge for himself. It is 

 to the great magnifying powers I am indebted; and every 

 one (with the same instrument) may prove the truth of 

 what I advance. 



I shall divide the stem of trees into 6 parts; 1st the rind; Division -of tfee 

 2nd the bark and inner bark; 3d the wood; 4th the spiral stem * 

 nerves; 5th the nerves or circle of life; 6th the pith. 

 The rind is I conceive merely an outward covering to the 

 free, to preserve its moisture, that the sun may not evapo- 

 rate its juices. It is true, that the same is continued 

 under ground ; but it may be as useful there to prevent the 

 entrance of the dust and earth, and pressure of stones, or 

 the injury of insects. It is composed of rows of cylinders 

 with a single line to divide them, and they are filled with a 

 clear and pellucid liquor. There are seldom more than four or 

 five layers of vessels ; but it is in general so covered with 

 parasite plants, and powdered lichens, that its thickness is 

 often more than doubled ; and it is not fit for examination, 

 till divested of all extraneous matter. It is the rind Division of -tire 

 thickened that forms much of the armature of plants. It rmd * 

 ^appears by no means necessary to plants, as there are a 

 number in which the bark serves as a covering instead of a 

 rind ; it is not therefore essential to them. Though to trees 

 it must be so reckoned. 



2d The bark and inner bark, though certainly very dif- Divisions of the 

 ferent as to form, are the same in juice ; and being so nearly bark * 

 allied, I shall treat them as one. They are truly of the 

 first consequence in the tree. They are the origin of the 

 leaves; the lengthened vessels of the bark and inner bark, 

 forming the interlacing vessels of the leaf, while the juice 

 concentrated and thickened produces the pabulum of the 

 leaf, as I endeavoured to show in my last paper. The 

 juice of the bark is I conceive the blood of the tree. It is 

 here alone are produced the gums, the resins, the oil, the 

 milk, in short all that truly belongs to the tree; gives taste 

 to it ; all I conceive that makes one plant different from 



another; 



