1897] NORMAL AND DISEASED ORGANS OF ABIES BALSAMEA 335 
wood continues in its greater growth in width, producing the 
so-called boil or tumor. The growth in width of the secondary 
cortex of the tumor is greater than at any other part of the 
affected branches. The diseased branches have a greater diam- 
eter, but are shorter than the normal lateral branches. They 
have a reddish color, differing from the normal branches, which 
are yellowish brown. Although the diseased shoots are shorter, 
the number of leaves does not vary much from that of the 
normal 
_ Outer bark—The epidermis does not vary much from the 
normal, except that epidermal hairs are rarely present. When 
present the hairs are usually only one-celled, agreeing in this 
respect with the terminal shoots, where epidermal hairs are absent- 
The periderm is more developed. It consists of from 8 
to I0 rows of cells the first year, which number is greatly 
increased during the second and later years, when the cork cam- 
bium gradually extends inward, and finally cuts off the primary 
cortex. In the tumor the cork cambium often extends as far as 
the secondary cortex during the first year of the infection. The 
cork cells are larger than the normal. 
_- Primary cortex —The cells of the collenchyma layer under the 
periderm are fewer in number, as well as less thickened. The 
chlorophyll parenchyma of the primary cortex contains no chlo- 
rophyll, but contains, at all seasons of the year, larger quantities 
of starch and tannin. More of the parenchyma cells become 
either thick walled or sclerenchymatous. The sclerenchyma 
| cells branch more profusely, especially in the first year’s shoot- 
The mucilage cells are smaller, as well as fewer, and do not 
increase in size with the increase in age of the branch. Fewer 
of the parenchyma cells contain crystals of calcium oxalate, 
but the number of tannin cells is greatly increased. 
oA The resin canals are present in greater numbers, and vary 
‘More in their size and form, as well as in the number and size of 
their epithelial cells. The second layer of cells is less thick- 
: ened. Since the growth of the periderm is greatly increased, 
_ and the formation of cork layers begins earlier in the affected 
