206 
MORPHOLOGY 
them a beaklike projection of the endosperm, a structure that char- 
acterizes Ginkgo. No seeds have been found containing embryos ; and 
since the same fact is true of 
the Cycadofilicales, it is evi- 
dent that all the seed plants 
of the Paleozoic shared this 
peculiarity. 
Conclusions. A summary 
of the characters of Cordaitales 
shows an interesting combina- 
tion. There are primitive 
characters which indicate con- 
nection with the Cycadofilicales 
and the cycad line, such as the 
large pith, the structure and 
mesarch bundles of the leaf, 
the structure of the ovule, and 
the swimming sperms. The 
advanced characters are the 
lofty and branching habit, the 
thick cylinder of secondary 
wood, the form of the leaves, 
and the compound ovulate 
strobilus, all of which are char- 
acters of the Coniferales. It 
FIG. 463. Section of ovulate strobilus of 
one of the Cordaitales, showing the large over- 
lapping bracts, in the axils of two of which there 
appear short branches bearing terminal ovules; 
that to right also shows a bract let. After 
RENAULT. 
FIG. 464. Pollen grains of one 
of the Cordaitales, showing the group 
of internal cells that probably belong 
to the male gametophyte. After 
RENAULT. 
seems evident, therefore, that the Cordaitales represent a second great 
branch from the Cycadofilicales stock, a branch which leads towards 
the Coniferales. This branch seems to have separated from the 
Cycadofilicales long before the other branch which ends in the modern 
Cycadales. 
