1906] JEFFREY & CHRYSLER—CRETACEOUS PITYOXYLA 13 
foliage, etc., there are now definite records, based on internal struc- 
ture, which carry the group far into the past. KNowLron™ has 
recently described an abietineous wood from the Jurassic beds of 
the Black Hills of Dakota which he calls Pinoxylon dacotense. It is 
characterized by the possession of vertical resin canals only, which 
are numerous and may occur in any part of the clearly marked annual 
rings. The structure of the tracheids and rays is that of the Abiet- 
ineae. This author does not mention the presence of marginal ray 
tracheids, and in view of the fact that he describes the wood as 
admirably preserved, they probably may be considered to be absent 
here as in our Cretaceous Pityoxvla. 
The Pityoxylon Conwenizianum of GoEPPERT from the ee 
boniferous of Waldenburg,'5 which has often been called in question, 
has received full confirmation from the description of a similar 
type of Pityoxylon, P. chasense, by PENHALLOw'® from the Per- 
mian of Kansas. In these two species vertical resin canals are 
said to be absent, although the horizontal canals of the fusiform 
rays are clearly present. There is, accordingly, every reason to 
believe that the Abietineae are a very ancient group in their first 
appearance. In fact, they may be traced geologically quite as far 
back as the Araucarineae, which it is customary at the present time 
to regard as the oldest of the Coniferales. That they are not more 
‘numerously represented in the Mesozoic and earlier strata is probably 
entirely a matter of antisepsis, since araucarineous remains are 
in general much better preserved than are those of the Abietineae, 
where they are found imbedded together in the same strata. Men- 
tion need not be made here of the Pityoxylon eggense (Witham) 
Kraus and Pityoxylon Hollicki Knowlton,*’? since both of these 
appear to have been in a bad state of preservation. 
The peculiar structure of the wood of Pinus in the Go cconus, 
as distinguished from that found in the case of Tertiary and living 
pines, probably affords an explanation of the greater vigor of the 
14 U. S. Geol. Surv. Ann. Rept. 207: 420-422. 1898-1899. 
15 GOEPPERT, Revision meiner Arbeiten. 
r6 North American species of Dadoxylon. Trans. Roy. Soc. Canada II. 64:76. 
1900. 
17 Trans. N. Y. Acad. Sci. 16:134-136. 
