268 BOTANICAL GAZETTE [APRIL 
Conclusions 
The following general phylogenetic conclusions may be drawn 
from a study of the leaf trace and foliar bundle of vascular plants. 
The primitive foliar bundle was a single monarch and mesarch 
vascular strand. This has persisted in the leaf trace of all the 
Lycopsida and in the blade of many of them, thus furnishing 
further evidence of the unity of the group and of its relatively 
primitive position. 
This type of bundle is present at the base of the leat trace In 
the Osmundaceae and in certain of the Ophioglossaceae, which 
thus seem to have been early separated from the other ferns. 
The leaf bundle of the primitive palaeozoic Filicales was a diarch 
and mesarch one. By the disappearance of its centripetal wood, 
this has given rise to the endarch foliar strands of living ferns, 
which have apparently been derived from the more ancient of the 
Botryopterideae. 
The diarch and mesarch leaf bundle is also the primitive one for 
the seed plants, which were developed along two main lines ie 
forms related to the early Botryopterideae, but which had acquired 
the seed habit. The members of the first series, including Cala- 
mopitys, Lyginodendron, and Heterangium, show the fern tendency 
for the protoxylem of the stele and leaf trace to become contin 
and in seriation with the centrifugal wood, and for an ultimately 
endarch condition to result. The other series, which includes 
all remaining gymnosperms, and probably the angiosperms, shows 
in its earliest and most primitive forms the tendency in the vasculat 
system of the stem and leaf for the protoxylem to become on 
ous and in seriation with the centripetal wood, and for an ultimately 
exarch condition to result. . 
These two groups are also clearly separated on other evidence. 
The endarch series are very fernlike in habit, possess seeds of a 
peculiar type, and show in their petiolar bundles (at least ™ 
Lyginodendron) that ancestral mesarch condition of the Botty- 
opterideae where the protoxylem shows no preference for er 
the inner or the outer wood. The early members of the scat 
group, however, such as Medullosa, do not show such <_ 
resemblances to the ferns, possess seeds of a higher and mo 
