342 
Wernham .— The Morphology of 
The vascular system of the strobilus-axis thus appears to be an 
aggregation of sporophyll-traces; but at the extreme tip, above the level 
of departure of the highest sporophyll, a few xylem-elements are still to 
be seen in section, so that the system is in reality cauline in origin. 
Summary of the Internal Structure. 
The vascular system is embedded in closely packed parenchymatous 
tissue. The parenchyma is remarkably homogeneous in tuber, root, stem, and 
in the peduncle and axis of the strobilus ; the sole differentiation is in the 
peripheral layer of empty, radially elongated cells, with thickened walls; 
the parenchyma, moreover, which is in immediate association with the stele, 
is more compact and of smaller cells than that of the main body of the 
cortex. The latter is traversed by large intercellular spaces. This 
peripheral layer is fairly constant in sections taken at all levels, and in all 
parts of the plant. 
There is no indication of an endodermis, except in the root. 
The vascular tissue consists of xylem only (except perhaps in the leaf). 
This is, for the most part, of typically scalariform tracheides. 
The general course of the vascular system is briefly as follows : That 
of the lower portion of the stem is a medullated protostele, which breaks 
up below into the strands which supply the roots on the one hand, and the 
young tuber on the other. The leaf-strands are continuous with those of 
the roots, and leave the stele without causing any disturbance in its 
continuity. 
The xylem on the side of the ring which faces the tuber rapidly thins 
out in an upward direction, and a level is soon reached at which there is 
a definite gap in the stele, so that £ pith ’ and cortex become continuous. 
Before this gap is reached, a xylem-strand, corresponding in position to 
that occupied by the strand of the young tuber at a lower level, leaves the 
stele and takes a central course into a hump of tissue (k, in Figs. 3 and 6), 
which seems to represent what Bertrand calls the * organ of Mettenius ’ ( 5 ); 
both hump and strand, however, soon disappear from the transverse sections 
as they are followed upwards. 
The U-shaped stele breaks up above into the isolated peduncle-strands, 
each of which goes to supply a sporophyll. One or two, however, appear 
in transverse section above the level of the last sporophyll. 
General Discussion of the Details observed. 
1. The noticeable U-form of the upper part of the stem-stele is, 
perhaps, the most striking feature ; it has no parallel in other Lycopodiaceae. 
It suggests, rather, an analogy to the upper part of the stem in Tmesipteris , 
in which the original protostele is disturbed by the outgoing leaf. As 
Bower points out, a similar appearance is seen in Ophioglossuni Bergianum , 
