14 hoes BOTANICAL GAZETTE [JULY 
genus ‘under modern conditions. It is generally inferred that genera 
which flourish under modern conditions cannot be of very ancient 
origin: This generalization, however, cannot be accepted in 
the case of Pinus, which, although found actually abundantly 
throughout the northern hemisphere in from 80 to gO species, can 
be traced in obviously allied genera back to the Carboniferous. 
The appearance of marginal ray tracheids about the beginning of — 
the Tertiary epoch, with the resulting improvement of water-supply, 
in all probability explains why so comparatively large-leaved a conifer 
should have been able not only to live on into the modern period, 
but to flourish as it never had before. Even at the comparatively 
early epoch of the Baltic amber beds (probably Eocene), there were 
numerous species present in the somewhat restricted area repre- 
sented by that formation. 
CONCLUSIONS. 
1. The woods of certain pines of the Middle Cretaceous of Staten 
Island differed from those of existing pines (a) in the absence of 
marginal tracheids in the rays; (6) in the highly resinous nature 
of the rays; (c) in the association of characteristic features of the 
hard pines, as exemplified by leaf-fascicles, cone-scales, and struc- 
ture of the primary wood, with the numerous tangential pits of the — 
autumnal wood which are a feature of the living soft pines. 
2. These features of difference from modern pines are probably 
GP ete AEA DST oo eee ee ee 
= esa 
- ~ STeie, 
to be regarded as ancestral, since they persist clearly and strongly in : 
the structure of the wood of the cones of the living species. 
3. The appearance of marginal tracheids in the rays of Pinus © 
is comparatively modern and does not in all probability antedate — 
the Tertiary. It. probably explains the greater prosperity of the 3 
genus in recent times. 
4. Another species of Pityoxylon from Scituate, Mass., has 
been described, which has the general features of the Pityoxyla of | 
Staten Island... It is not possible, however, to refer it definitely te. 
Pinus, nor is its geological horizon settled. . 
In conclusion we Wish to offer our warm thanks to Dr. HoLLick i 
for many kindnegses in the matter of securing material. 
HARVARD UNIVERSIry. 
