1915] BURLINGAME—ARAUCARIANS 107 
modern ones.. This would strongly indicate parallel development 
of similar structures in the two groups. On the evidence, then, as 
it stands, we must decide that the cordaitean theory is much the 
more probable. 
In respect to the abietinean theory we meet a different state of 
affairs. It is not claimed that Abietineae are more like cordaiteans 
than araucarians, but that it can be shown that the likenesses of the 
latter have been secondarily acquired. This is not parallel develop- 
ment. The theory assumes that a considerable number of char- 
acters underwent extensive modification during the evolution of 
the primitive conifers (that is, abietineans). Multiseriate bordered 
pits of the cordaiteans became uniseriate, remote, and rounded. 
The thin-walled unpitted ray cells became thick-walled and pitted. 
Resin canals were evolved. Then this primitive stock is conceived 
to have split into two lines, one of which continued its evolution 
along the same lines as the parent stock. The other line (arau- 
carians) faced about and began the reacquisition of the characters 
that had been lost. It almost completely regained the original type 
of pitting, lost all trace of its pitted rays, and almost totally lost 
the ability to produce resin canals in the wood. The history of 
other characters is much the same. The adherents of this theory 
do not seek to deny these resemblances nor the necessity of showing 
that they have been secondarily acquired. I have already set forth 
the evidence through which they believe that they have proved 
this astounding evolutionary sequence. So far as resemblance 
or likeness goes, the cordaitean theory is far and away the more 
probable. 
On the basis of fossil history there is not much to choose in 
respect to antiquity of the two families, though the Araucarineae 
have, perhaps, at present the more certain record in the older 
rocks. Still, specialized abietineans are known so far back that 
we must assume their origin to have been very much farther back. 
I shall speak of the bearing of the transitional fossils of the Mesozoic 
after discussing the remaining canons of evidence, because it is 
only in the light of the inferences made in accord with them that 
these fossils can be made to support this theory. On the basis 
of geological sequence they favor the cordaitean theory, inasmuch 
