NOTES ON THE ANATOMY OF THE PUNCTATUS GALL 537 
was unable to explain their origin. It is evident that he searched 
carefully for the beginning stages of such but did not succeed in 
finding them. Krick (11, p. 17) has also found somewhat similar 
bodies to be normally present in the bark of the red beech, some of 
which had cork for a central nucleus while still others had wood. It 
is possible that many of these woody complexes in the bark may origi- 
nate from misplaced cambium cells. Such is ev^idently the case in the 
galls caused by the black knot fungus on the choke-cherry (Stewart 20, 
pp. 1 1 9-1 20). 
With the possible exception of the pine, it is likely that the struc- 
ture of no wood is better known generally than that of the oak, as 
both of these woods are usually studied in elementary courses in plant 
histology in institutions where such courses are offered. The results 
of a large amount of investigation have been published on the struc- 
ture of oak wood but to attempt to enumerate all of these would be 
superfluous in this article. Hartig (9, pp. 92-96) gives a rather de- 
tailed account of the structure of this wood, and Bailey (2 and 3), 
Bailey and Sinnott (4), and Eames (7), treat the ray structure rather 
exhaustively. 
Normal oak wood is composed of vessels, tracheids, fibers, and 
parenchyma cells, the last of which occur both as wood and ray 
parenchyma. The vessels are very large and there is a tendency for 
them to form scalariform perforations according to Solereder (19, 
p. 781). In some species, especially those belonging to the white oak 
group (subgenus Lepidobalanus) , the vessels become filled with tyloses 
after a time. Gerry (8, pp. 451 , 455-456) has recently done some work 
on the subject of tyloses and finds that in contrast with the white oaks 
the members of the red-oak group (subgenus Erythrobalanus) are 
normally free from tyloses with many exceptions. Tyloses occur 
scattered or frequent in the sap wood of Quercus velutina and scattered 
in the heart wood. In the closely related scarlet oak Q. coccinea they 
are usually scattered but may be abundant in connection with fungus 
growths. The formation of tyloses is easily induced through the 
wound stimulus. Gerry (8, p. 447) found that even the wound pro- 
duced by felling the tree may cause the formation of tyloses in the 
outer rings of Q. michauxii. 
Dorranca, who is completing a translation of K lister's Pathologische Pflanzen- 
anatomie, has been kind enough to supply me with some of her translations of this 
and closely related terms. Among these are: knarl, ball, and ball-formation. 
