180 General Notes, [ Feb. 
tudinal sections showing large numbers of dividing nuclei. At 
this time. the ground tissue composed the greater part of the 
stem, though the vascular system had increased considerably. 
Soon the growth in the cortical and medullary tissues almost 
entirely ceased. May 27, cell-division had so nearly ceased in 
these tissues that I could find no dividing nuclei, though I spent 
much time looking for them; and in the same material cell- 
division was taking place along the cambium line. 
But growth does not entirely cease, at least in the outer cortex, 
for I found cell-division here in a three years’ growth. 
ig. 3, a, is a camera drawing from near the epidermis of a 
three-year-old stem, showing a nucleus that has divided and the 
new cell-wall just formed. I think, in this tissue, growth con- 
contained protoplasm and nuclei. I do not think the central 
cortical tissue lives very long, though I found some cells of a 
four years’ growth containing protoplasm and starch. 
The main growth of the stem is along the line of cells desig- 
nated as the “ cambium zone.” On one side the cells that are 
here newly formed pass into the xylem, on the other into the 
As each year’s growth of xylem is much larger than 
that of the phlceum, many more cells must go to the formation of 
xylem than of phlceum. 
To all appearances, when the stem is growing, the cambium 
zone is but one cell broad, as all nuclei that show signs of division 
in this tissue are found along a straight line in a longitudinal 
- Fig. 3, c, is a longitudinal section through a three-year-old 
diameter of a cambium-cell, thus showing that there must be 
one year old, but in cells of the medullary rays passing through 
the zylem, and which were four years old, I found protoplasm 
~ Many cells of the phlceum, in all specimens examined, were 
