54 BOTANICAL GAZETTE [JANUARY 
Quercus to be of two sorts, linear or uniseriate, and broad or com- 
pound. In investigating the relative primitiveness of these two 
types, he examined a fossil oak from the Miocene. Here he found 
the same two sorts of ray, uniseriate and broad, but the broad rays, 
instead of being homogeneous masses of parenchyma, were com- 
posed of smaller rays, separated from each other by fibers, or by 
fibers and wood parenchyma. This condition lead to the suspicion 
that broad rays of living oaks might be derived from the aggrega- 
tion and fusion of small rays. Accordingly, he examined seedlings 
of a number of oaks, and found such to be the case. Seedlings of 
black oaks show, near the pith, a ray structure like that of the 
miocene oak, with a gradual, progressive fusion until a single, 
homogeneous, compound ray is formed. Seedlings of white oaks 
show a still more primitive condition. In some, for the first 15 or 
20 years, only uniseriate rays appear, which generally fuse into 
compound rays. Thus both anatomical and paleobotanical evi- 
dence point to the conclusion that for Quercus uniseriate rays are 
primitive, and that the large rays are formed by a process of fusion. 
This conclusion is further strengthened by a consideration of 
conditions found in wounded oaks. Bartey® of this laboratory 
investigated a number of species of this genus, and found that in 
every case, after a severe wound, a broad ray breaks up into a 
number of uniseriate or small rays, a clear case of traumatic 
reversion. 
This compounding process BAILEY has examined in a number of 
genera of the Betulaceae and Fagaceae, with similar results. For 
example, in Alnus? he finds all types, from exclusively uniseriate 
rays in A. acuminata H.B.K. to completely fused aggregate or 
compound rays in A. rhombifolia Nutt. 
The uniseriate rays of Aesculus, therefore, are open to two inter- 
pretations; they may be primitive like those of white oak seedlings, 
in which case Aesculus has a very low type of wood structure; or 
they may be the result of reversion, in which case Aesculus is 
6 Bartey, I. W., Reversionary characters of traumatic oak woods. Bor. GAZ. 
50:374-380. pls. II, 12. 1910. 
7 BarLey, I. W., Relation of the leaf trace to the origin and development of com- 
pound rays in the dicotyledons. Ann. Botany (ined.). 
