VOLUME XLIX NUMBER 3 
BOTANICAL Gazette 
MARCH 7910 
ON THE ORIGIN OF THE BROAD RAY IN QUERCUS 
CONTRIBUTION FROM THE PHANEROGAMIC LABORATORY 
OF HARVARD UNIVERSITY NO. 17 
ARTHUR J. EAMES 
(WITH PLATES VIII AND Ix) 
As is shown in Kwny’s Botanische Wandtajeln, nos. 75 and 76, 
the wood of Quercus consists of vessels, tracheids, fibers, and paren- 
chyma. The last is disposed in two systems: the vertical, consisting 
of more or less scattered rows of cells, forming the xylem parenchyma; 
and the horizontal, made up of plates of cells extending radially, 
the medullary rays. The latter are of two sorts: small, numerous 
rays, which are thin sheets of tissue, linear, and of a single row of 
cells as seen in transverse and tangential sections; and occasional 
broad, generally fusiform masses, many cells wide, which form the 
most prominent feature of oak wood, its remarkable “silver grain.” 
In our first two figures both kinds of rays are seen: fig. 1 shows in 
transverse section a portion of a large ray, and of several small ones 
from the wood of Quercus rubra; and fig. 2, the tangential view of 
similar rays in the same species. 
In the study of sections of a fossil oak from the gold gravels of 
California (Miocene), the material for which was kindly loaned the 
_ Phanerogamic Laboratories of Harvard University for investigation, 
an unusual ray structure was noticed. The uniseriate rays are 
present as in the living oaks; the large rays, however, are not homo- 
geneous masses of parenchyma, but are represented by groups of 
sm*ller rays. Fig. 6 shows such a group in tangential view. The 
smaller rays are so arranged as to form, in aggregate, the elongate 
fusiform mass of the normal large ray. They are separated from 
each other, however, by fibers, or by fibers and wood parenchyma. 
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