28 GROWTH OF WOOD IN THE STEM. 
year’s growth: b. answers to that part which is nearest 
the outside of the stem, and is a mass of young green 
bark; at f. 2. the same stem is seen cut lengthways, 
and the same letters signify the same parts; f. 3. is a 
magnified view of a cross, or horizontal section of a 
maple stem, four years old; exhibiting at p. the pith; 
at 1. the wood, formed during the growth of the first 
year; at 2. that which was formed during the second ; 
at 3. that during the third; at 4. that during the 
fourth year; at 0. is seen the Bark, and between the 
bark and wood at ¢. a quantity of green matter, which 
will form the wood of the fifth year. 
Each year a fresh layer of wood is added to every 
part of the tree, and as some parts are older than 
others, so these will be found to possess more wood ; 
the wood deposited, is added outside that which is 
already formed; and the next year’s wood will. be 
added, or deposited outside that which is formed this 
year, and so on; each layer of wood being younger 
than that which has gone before. A fine line separates 
the different layers from each other, and the number 
of years the branch, or stem, has been growing, can 
be reckoned by counting the layers, or rings of wood 
which exist in it. At f. 4. is represented a cross, and 
lengthways cutting of a piece of wood, which has been 
seven years growing; at p. is seen the pith; 1. shows 
the wood of the first year’s growth, surrounding the 
pith; 2. that of the second year, which will be seen to 
surround the wood of the first; 8. that of the third 
year, and so on; the bark in this figure has not been 
represented. 
