334 BOTANICAL GAZETTE [NOVEMBER 
ately below the pith diaphragm. The greater number of these 
cells remain thin walled. Isolated cells often become thickened 
but not sclerenchymatic. 
The internodal pith is made up of thin walled parenchyma 
cells and areas of sclerenchyma. The parenchyma cells are 
from 2 to 4 times as long as wide. They are polygonal in cross 
sections and rectangular in longitudinal sections. Isolated paren- 
chyma cells often become thick walled in older internodes. The 
sclerenchyma cells are cubical and smaller than the parenchyma 
cells. They are provided with pore canals, and the thickening 
often extends inward so that the whole cell lumen disappears. 
The cells are arranged in definite areas extending from the 
periphery of the pith toward the center. Many of the scleren- 
chyma areas extend across the pith, thus forming a kind of 
diaphragm of mechanical tissue which alternates with areas of 
thin walled parenchyma. 
2. Diseased shoots and branches. — The normal terminal shoots 
differ from the lateral, not only in that they are negatively 
geotropic, but also in the greater or less development of their 
different morphological units. The diseased shoots in many 
respects have characters similar to the normal terminal shoots. 
In comparing, therefore, the anatomy and morphology of the 
diseased shoots with the normal, the terminal shoots should also 
be considered. Hartmann?5 makes a comparison of the diseased 
with the lateral normal branches only of A. pectinata. 
The affected branches, like the terminal, are negatively geo- 
tropic. Cross sections of the first year’s shoots show a greater 
development of primary cortex and pith, while the secondary 
cortex and wood, in proportion to the former, are less developed, 
about the same as that of the lateral branches. In the second 
year of the diseased branches changes occur, which are more 
marked, especially in the increased growth of the periderm, 
wood and secondary cortex.’ The wood reaches its maximum 
growth during the second year. This is true of all the affected 
branches above the tumor. At the first point of infection the 
|S Mbid., p. 35- oy 
