cen ag BOTANICAL GAZETTE [JUNE 
of fibers into parenchyma cells. This figure represents in tan- 
gential view the wood of the root of Gaylussacia, a genus closely 
allied to Vaccinium and having identical ray structure, as is seen 
by the comparison of the two woods illustrated in figs. 7 and 9. 
Fig. 10 is a tangential view of the wood of the root of Rhododen- 
dron, a genus also allied to Vaccinium although not so closely as is 
Gaylussacia. The wood as shown here is much like that of the 
northern oaks, especially in the marked contrast between its large 
and smallrays. The construction of the ray itself in Rhododendron, 
however, is more clearly seen in fig. rr, a transverse section of the 
same wood. The interspersion of the light colored fibrous elements 
through the ray at once shows its composite character, and although 
it does not illustrate actual transformation of fibers into radial 
parenchyma, it points the way to that as a natural solution of the 
origin of the broad ray in this genus. 
In regard to Vaccinium and the allied Gaylussacia it is now 
clear that the large rays in these genera are of the same nature as 
those of Quercus, and like them are in strong contrast to the more 
numerous uniseriate rays. In Rhododendron also we noted the 
same condition, albeit its origin was not in all respects so clear. 
That this condition of Vaccinium and allied genera, which is so 
similar to that found in the oak, is not common to all ericaceous 
woody types, is evidenced by fig. 12, which shows in tangential 
view the wood of the stem of a species of Arbutus. The rays: of 
this wood do not fall into two strongly contrasting categories, 
the broad and the uniseriate. Rather do they grade into each 
other and are only relatively broad or narrow when compared with 
each other. In this respect Arbutus presents the general situation 
for forest trees, the majority of which do not possess contrasted 
broad rays and uniseriate rays, but have all their rays comparatively 
small and of intergrading dimensions. 
From this examination of the genus Vaccinium and other genera 
allied to it, and the comparison of them with the wood of Quercus, 
we must conclude that the well known large rays of the latter 
have their counterparts in the somewhat smaller rays of Vaccinium 
and Gaylussacia. These rays, although of considerably smaller 
dimensions, are in just as marked contrast to the accompanying 
