993 
Medullary Rays of Quercus. 
I will first trace out a series in which the transverse division by fibres 
is increasingly marked. The following descriptions refer to the tangential 
view of the rays, and describe only certain of the several types of rays 
occurring in each species. 
Series I (Deciduous with high rays). 
Q. Macdonaldi (Fig. 13): ray very high and broad. 
Q. Durandii , Buckl.: ray very high, crossed at long intervals by thin 
interrupted transverse lines of fibres. 
Q. aquatica , Walt. : ray very high, thinner than those of Q. Durandii^ 
divided by transversely oblique bands of fibres. The bands are separated 
by very long or by shorter intervals ; they are thin, often biseriate, though 
sometimes they consist of more than two ranks of fibres and are then ‘frayed ’, 
that is to say, they include gaps which are occupied by ray-parenchyma. 
Q. acuminata , Sarg. 1 (Fig. 14) : rays at about the same stage as in 
Q. aquatica , but vertically superposed rays occur here and there. 
Q. bicolor , Willd. (Fig. 15), and Q. garryana , Dough, have high 
vertical rays, as well as vertical series of rather broad rays, which are 
separated from one another by thinner or thicker bands of transversely 
oblique fibres, so that in the latter case it is difficult to decide whether the 
ray should be described as divided or the rays as superposed. 
Series II (Deciduous with slender fusiform rays). 
The high rather slender fusiform rays seen in places in Q. bicolor and 
Q. garryana lead to the high somewhat plumper ones of Q . sessiliflora , 
Salisb. (Fig. 15), some of which are feebly divided by a few fibres. At 
about the same stage are the rays of Q.hetcrophylla , Michx., and some in Q. 
undulata , Torr., but the latter also shows rays divided at intervals by thinner 
or thicker bands of transversely oblique fibres. Q. georgiana , M. A. Curt. 
(Fig. 17), has true undivided narrow fusiform rays which are often ranged in 
vertical series, the successive rays being separated by solid or frayed bands 
of fibres. 
Series III (Deciduous with broader fusiform rays). 
Series II with rather slender fusiform rays is paralleled by another 
series with broader fusiform rays. These are undivided in Q. Kelloggii 
(cp. PI. LXXVI, Fig. 19), but are feebly divided by occasional transversely 
oblique thin bands of fibres in Q. texana , Buckl., and Q. Douglasii , Hook, 
et Arn. (PI. LXXV, Fig. 18), both of which also show vertical or slightly 
obliquely vertical series of close-set superposed rays. The difficulty of 
distinguishing descriptively between a divided ray and a series of superposed 
1 I do not know what the correct name of this American oak should be, as the true Q. acumi¬ 
nata is an Indian species described by Roxburgh. 
