1915] BURLINGAME—ARAUCARIANS 17 
tinguishable in the two families. The essential feature is that the 
mass of the wood, apart from the medullary rays, is composed of 
tracheids with multiseriate bordered pits on their radial walls” 
(53, p- 654). 
The more recent and comprehensive argument for this view 
is that of THomson (70). His arguments may be summarized 
under four heads: (1) the Araucarineae closely resemble the Cor- 
daitales in the anatomy of the stem, root, and leaf; (2) they are 
the oldest known conifers; (3) certain mesozoic forms show a transi- 
tion from Araucarineae toward Abietineae; (4) vestigial structures 
in leaf, stem, root, and reproductive axes, some of which indicate 
(a) the origin of araucarians from cordaiteans, and (0) others of 
which indicate the origin of Abietineae from Araucarineae. 
Although I have not seen the papers by GoTHAN (21, 22), the 
references to them by other writers, particularly JEFFREY and 
THOMSON, would indicate that he holds similar views respecting 
the relationship between the Araucarineae and Abietineae. 
Speaking of the pith, THomsoNn (70) says: ‘In the variability 
of the size of the pith, and in the magnitude which it may attain, 
the Araucarineae are the only forms of the conifers at all com- 
parable to those of the cordaitean alliance.” 
The root is usually diarch, and the protoxylem points are 
separated into two forks by the presence of a resin duct, as in the 
Pineae (70); nor “is there any indication of a resin duct in the 
center of the metaxylem, as in the Abieteae.” 
There is a very broad transitional zone from the primary to 
the secondary wood in the stem and particularly so in the cone 
axis. “In no other group of the conifers is there an approach to 
this cordaitean condition” (70). 
There are many resemblances between araucarian and cor- 
daitean leaves. The araucarian-podocarp alliance includes the 
only conifers with leaves at all comparable in size to those of the 
cordaiteans. In both, the leaves persist for many years; in both, 
the leaves are parallel and dichotomously veined, with mesarch 
collateral bundles and remarkably persistent leaf traces. 
Although the pitting of the more ancient araucarians was so 
nearly identical with that of cordaiteans, it “is much reduced in the 
