1 6 ALB AN STEWART 
from the tracheids of this gall. If they are invariably present I have 
not always been able to see them. They are probably sometimes 
absent. Thomson (i6, p. 22, pi. 4, fig. 36a) has found a somewhat 
similar condition, as he states that "where the pits are multiseriate, 
as in young root wood, ' Larix americana' there may not be a trace 
of the bar of Sanio." 
The walls vary in thickness, individual tracheids showing differ- 
ences in this respect. This condition is very noticeable in longitudinal 
sections, but it is less marked in cross sections (see plate I, figure i). 
The walls are often sinuous (figure 4), causing wide and narrow 
places in the same tracheid. Where this condition is pronounced 
inflations in the walls may result from it. Blunt end walls are 
common. The length of the tracheids varies greatly and as a whole 
they are shorter than in normal wood. Cells which are isodiametric 
or nearly so occur commonly, which show their tracheary character 
in the pitting. Wornle (18, p. 132) has described similar cells near 
tl^ broad rays in juniper stems infected with Gymno sporangium 
umperinum. The formation of these short tracheids possibly comes 
about by the cross division of cambium daughter cells. Such is the 
case in traumatic wood according to de Vries (5, p. 21). 
Cells occasionally occur which have the character of both tracheids 
and parenchyma cells as the pits in one part of the wall are bordered 
and in another part plain. The plain pits occur in such places as to 
leave no doubt about their true character. They were not mistaken for 
one-sided bordered pits as they do not occur in opposite rays. Maule 
(11, p. 5, plate II, figure i) describes and figures cells.somewhat similar 
to these in the traumatic wood of Abies cephalonica, Thompson (15, 
p. 336) describes transitional cells which are normally present in the 
rays of Abies homolepis, and Groom and Rush ton (7, p. 474, figure 16) 
mention simple pit-like structures between the bordered pits in Pinus 
excelsa, a species from the Himalayas. True wood parenchyma cells 
also occur in this gall, which have nuclei and other protoplasmic 
contents. Such cells do not occur normally .in the pines according 
to Penhallow (13, p. 112). They appear to be more numerous among 
the tracheids which first bend outward from the normal wood into 
that of the gall, but this may be due to the fact that there is less resin 
in these parts so that they can be more readily seen there, and their 
true character recognized, than deeper in the gall. 
Cross sections cut through the center of the gall usually show that 
