Wound healing m a species of Oak. 11 
by the additional development of callus-wood from the edges of the 
wound as in the present instance. 
The wound-wood in the vicinity of the rind-galls was also 
examined in some detail, longitudinal sections as well as trans¬ 
verse being cut where possible. A considerable increase in the 
amount of wood parenchyma was observed, also the smaller size 
and more scattered arrangement of the vessels in these regions. 
The cavities of the vessels were frequently found to be completely 
blocked with much thickened, lignified tyloses flattened by pressure 
into polyhedral forms and communicating with one another by 
means of simple pits. Near several of the wounds these tyloses 
were packed with starch grains. Thinner-walled tyloses were found 
to be very abundant in the sap-wood lying to the outside of the 
embedded peg. 
As the tissue of the overarching callus-cushions is much 
distorted, sections were cut to the right and left of the injuries 
described above, so as to show the wound-wood in continuity with 
the normal wood. In several cases the disintegration of a broad 
ray into a pencil of uniseriate rays was found to occur as the result 
of the injury, and the gradual compounding of these was noticed. 
In other cases, however, the rays continued their course undisturbed 
by the wound-stimulus. 
The xylem formed outside the wounded areas after the coal¬ 
escence of the callus-cushions was also examined. In most cases 
the wound-wood in these regions showed only non-aggregated 
small rays. Fig. 2 (Plate II), is a photomicrograph of a transverse 
section through the wound-wood outside the peg, just where heart- 
and splint-wood join. Owing to the presence of dark-brown tannini- 
ferous contents in the ray-cells, the compounding process can be 
seen very distinctly. The abrupt formation of broad compound rays 
was also noticed in the straight grained tissue near several of the 
injuries, and the same phenomenon was observed in most of the 
callus-cushions. 
During the last two years much has been written regarding the 
evolution of the different types of medullary rays met with in 
Dicotyledons and more especially in the Fagales. 1 Eames, 2 from 
the study of ancestral forms and the development of seedling oaks, 
has supported the view that the wood of primitive Fagaceee was 
entirely devoid of the broad homogeneous “primary rays,” which 
are present together with uniseriate rays in the wood of deciduous 
1 See “ Medullary Rays and the Evolution of the herbaceous habit.’’ 
New Phyt., Vol. X, p. 362. 
* Eames, A. J. “On the Origin of the Broad Ray in Quercus." 
Gaz., 49: 161 166. 
Bot. 
