Igt5] BURLINGAME—ARAUCARIA BRASILIENSIS 23 
exposed foliar organs. It is an interesting and I think a significant 
question whether the pollination habit or the cones were developed 
first in this group. If we assume provisionally that the cone habit 
did not develop until after pollination was a fixed habit, the explana- 
tion of the origin of the latter given above might be applied to 
this group also. The cone habit would then have been acquired 
while the integuments and pollination apparatus were being per- 
fected. The difficulties of this explanation seem to me not to lie 
in its application to the Cordaitales themselves, but in the assump- 
tions that must be made in deriving the Coniferales, particularly 
the Araucarineae, from them. 
If it be supposed that the Cordaitales as a class had all reached 
essentially the same stage of development of the pollination devices, 
and that it was comparable to that already described for the 
Cycadofilicales, we may then seek to see just what changes must 
have taken place during the evolution of modern conifers. Ginkgo 
presents almost the same devices as the cycads, and we may there- 
fore confidently assume that an explanation that will suffice for 
the one will prove adequate for the other. 
CONIFERALES.—Excepting for the moment the araucarians 
and Saxegothaea, the modern conifers are characterized by the 
pollen being caught in a pollination drop and drawn down upon 
the tip of the nucellus or at least into the micropyle, where it 
germinates. The pollen tube that is produced is both haustorial 
and spermiferous. It grows more or less directly down through 
the nucellus and delivers the male cells in the neighborhood of the 
archegonia. It must be noted that it thus differs very sharply 
from the pollen tube of the cycads and Ginkgo, where the pollen 
tube is strictly haustorial and is never even entered by the body 
cell or its products. It is evident therefore that either this pollen 
tube is one that has altered its function and completely changed 
its method and direction of growth or it is a different kind of 
pollen tube. 
As there were no pollen tubes (probably) in the Cordaitales 
there is no compulsion to assume that their descendants neces- 
sarily developed a tube that behaved in the manner of the cycads. * 
Ginkgo, of course, would be an exception to this statement, but 
