538 
ALBAN STEWART 
Specimens of a number of the normal branches were taken from 
the tree from which the galls were collected to be used in comparing 
the normal wood with that of the gall. Without exception these 
specimens show tyloses to be present in the vessels, and their abund- 
ance in places leads one to suspect that they may not all have been 
normally produced. Possibly the gall stimulus has had something 
to do with their production. I have been unable to find any references 
in the literature on the anatomy of galls which records exactly similar 
conditions, but it seems to be an established fact that the stimulus 
resulting from parasitic fungi is capable of exerting an influence upon 
the structure of the host plant some distance beyond where the fungus 
actually occurs. The normal wood of Abies contains no resin canals, 
but Anderson (i, p. 465) found them to be present in all branches 
above parts infected with Aecidium elatinum. He also found (pp. 
473 > 476) that the branches of Pinus Strobus, Larix japonica, and 
Picea excelsa, which were situated above parts infected with Agaricus 
melleus, contained a greater number of resin canals than did the normal 
wood of these species. Mer (16, p. 367) also states that resin canals 
occur in the branches of Abies pectinata which are above parts infected 
with Phoma abietinae. Rather striking abnormalities may result 
from the wound stimulus some distance away from the actual wound. 
Maule (15, p. 12) found in Rosa centifolia that very broad rays and 
short wood cells persist 5-6 cm. from the wound, and De Vries (6, 
p. 20) found evidences of wounding in the structure of the wood of the 
Caragana aborescens 7 cm. from the wound. The above citations 
give sufficient ground for believing that if the tyloses in the branches 
of this oak result abnormally, the gall stimulus is the cause of it. 
The origin and structure of the broad rays in oak wood has been 
the subject of much study and discussion in recent years. As is well 
known, the rays in oak wood are of two kinds: those which are one 
cell wide in cross and tangential section, known as uniseriate rays, and 
those which are more than one cell wide. The rays of the second 
group can be further subdivided into those which are 2-3 cells wide, 
multiseriate, and broad homogeneous plates of parenchyma tissue, or 
compound rays. Of these three kinds, the uniseriate rays are usually 
considered to be the more primitive. 
Until rather recently the broad rays, the so-called primary medul- 
lary rays, have been considered to be inclusions of the fundamental 
tissue between the primary fibrovascular bundles. In his study of 
