Bower.—Studies in the Phytogeny of the Filicales. 505 
complexity of the leaf-trace these Ferns may be held as forming a series, 
progressive from the simple condition seen in the simpler Gleichenias, and 
leading to the state seen in Platycerium. It will be seen later how far 
this runs parallel with seriation of them according to other characters. 
It has been seen that branches are given off from the bases of many of 
the leaves, on the abaxial side (Fig. 1). In resolving the question of the nature 
of the branching, it is important to know the vascular connexions of the bud. 
This is shown for a given case of Cheiropleuria by the sections a-e of Text- 
fig. 7, which read from below upwards. The related leaf-trace originates 
from the axial stele in the normal way, and the protoxylem divides as usual 
as it enters the leaf-trace into two strands, which take the usual position. 
But the proportions of the leaf-trace strand are different from the normal. 
(Compare a , which is normal, with b, which bears a bud.) Its outline is 
% c 
Text-fig. 7. Transverse section of the rhizome of Cheiropleuria , to show the relations of the 
leaf-trace and the lateral bud to the stele of the axis, a shows the relation of two normal leaf- 
traces, where no bud is formed, b-e show successive sections from below upwards, in the case of 
a leaf-trace where a lateral bud is borne on the abaxial side of the leaf-trace, x 3. 
nearly circular (b), owing to an enlargement of the xylem on the abaxial 
side. Later the trace opens out, as in the normal leaf, on its adaxial face ; 
then, first on the one side and then on the other, lateral hook-like processes 
are formed (b, c). These soon become detached as the two components of 
the leaf-trace, and as such enter the petiole. The large residuum of vascular 
tissue, lying in the median position with regard to the leaf, passes out 
directly as the stele of the lateral axis ( d , e). The vascular relations are 
here essentially the same as those seen in Lophosoria , or Metaxya. As in 
those Ferns, so here in Cheiropleuria , the vascular connexions indicate that 
the lateral axis is an accessory appendage to the leaf. It would be difficult 
to see in them any evidence supporting the view that such branches are 
a result of some modified bifurcation. The conclusion will then be that 
dichotomous branching is in abeyance in Cheiropleuria, and that a forma¬ 
tion of adventitious buds at the leaf-bases is the rule. This conclusion is, 
however, provisional, pending a searching examination of the ultimate 
L 1 a. 
