1910] BAILEY—TRAUMATIC OAK WOODS 379 
botanical evidence, the large homogeneous masses of ray paren- 
chyma, or the so-called primary rays of oaks with deciduous 
foliage, appear to have been built up by an aggregation and fusion 
of numerous uniseriate rays. 
-5. Traumatic reversions are confined to regions which have been 
severely injured. Occasionally areas where the traumatic effect 
has been slight show an acceleration of the compounding process 
instead of a reversion to ancestral stages. 
6. The so-called primary ray is seen to have originated from an 
aggregation and fusion of secondary rays, and to be in no way 
related to inclusions of fundamental tissue between the primary 
fibrovascular bundles. From this phylogenetic relation of the 
two sorts of medullary rays it seems that the term primary is 
inadmissible entirely for the large rays of oak, and that the term 
compound might be advantageously substituted. 
In conclusion I wish to express my sincere thanks to Mr. G. B. 
SupwortH, dendrologist of the U.S. Forest Service, for material 
of Alnus rhombifolia. I am also much indebted to Professor 
E. C. Jerrrey for suggestions and advice, and to Mr. A. J. Eames 
for material of several wounded oaks. 
Harvarp UNIVERSITY 
CAMBRIDGE, Mass. 
EXPLANATION OF PLATES XI AND XII 
PLATE XI 
Fic. 1.—Quercus nigra: tangential section of the normal adult wood, 
showing the so-called primary and secondary rays; the vei are seen to 
- large masses of homogeneous ray parenchyma; 1 
- 2.— Quercus nigra» tangential section of the kissits wok showing 
ecistine mass of small rays; X 120. 
Fic. 3.—Quercus virginiana: tangential section ‘of the normal adult wood, 
showing strong evidences of a compounding ira, inclusions of fibers and 
Wood parenchyma cells occur conspicuously; 12 
Fic. 4.—Quercus virginiana: tangential seta of the traumatic wood, 
showing uniseriate non-aggregated rays in the immediate vicinity of a severe 
wound; X 120, 
Fic. 5.—Quercus densiflora: tangential section “ the normal adult wood, 
showing aggregating and fusing mass of small rays 
