NOTES ON THE ANATOMY OF PERIDERMIUM GALLS 15 
nate pitting. Illustrating of this tendency appears in plate I, figures 
3 and 4, which show about average conditions in this respect. A 
stronger tendency towards an alternate arrangement occurs sometimes. 
Rarely both an opposite and an alternate arrangement of pits takes 
place in the same tracheid wall and occasionally there are transitional 
stages between these two methods. Where the pits alternate they are 
sometimes slightly flattened by mutual contact. (See plate I , figure 3) . 
Thomson (16, p. 17) mentions alternate pitting in ihe cone axis and 
early wood of the Abietineae and that the pits are sometimes flattened 
by contact. He also shows on his plate IV, figure 36c, a tracheid 
from the young root wood of Larix americana in which there is a 
suggestion of both opposite and alternate arrangement of pits, a 
condition which is not strikingly different from what sometimes occurs 
in the gall under consideration. A slight tendency towards an 
alternate arrangement of pits is in reality not an uncommon feature 
in several species of pines. It occuis to a greater or less extent in 
P. echinata, P. lambertiana, P. palustris, and P. strobus. Occurring 
as it does in several species of pines it is very likely that careful search 
would reveal it in others. It probably has no great significance in 
Pinus. 
There is a great difference in the size of the pits in the tracheids. 
They are usually about normal in this respect, but sometimes there 
are bordered pits present which are very much smaller, often about 
one fourth the usual size. Large and small pits may occur closely 
associated in the same tracheid wall. The pits may be scattered 
or closely arranged (figure 4). 
According to Gerry (6, p. 122) the pines and other conifers with 
abietineous affinities always have bars of Sanio present in the walls 
of the tracheids, while in the Araucarineae they never occur. Jeffrey 
(10, 544-545), however, has subsequently found them to be present 
in certain regions of Araucaria Bidwellii and A. imbricata. By 
staining with Haidenhain's haematoxyHn and safranin according to 
the method described by Jeffrey (I.e., p. 547), these bars can be easily 
seen in some of the tracheids of the gall but they fail to appear in 
others. They may stand out sharply in one while in another adjacent 
tracheid they can not be seen, or, they may appear in one part of the 
wall and not in another. Very faint traces of them occur at times. 
As so much depends on the methods of staining in order to see these 
bars, it is hardly safe to say positively that they are absent at times 
