33 § Bower . — On the Structure of the Axis 
is certainly very striking, both as regards arrangement and 
structure, allowance being made for the much smaller size 
of the plant of P silo turn. The correspondence with Tmesi- 
p ter is is not so close ; M, Bertrand distinguishes under the 
name ‘ game protectrice ’ a somewhat irregular sheath sur- 
rounding the vascular stele \ after examining this sheath 
in various stages of development. I do not find the 
characteristic marking of the radial walls, nor is the sheath 
itself in any way clearly defined as regards arrangement of 
cells. In fact Tmesipteris appears in this respect to correspond 
to Lycopodium ; on the other hand, P 'silo turn and Lepidos- 
trobus Brownii , while they resemble one another in the details 
of the sheath, differ from Tmesipteris and Lycopodium ; the 
comparison with Selaginella as regards the sheath will be 
introduced later. Turning to the point of the presence or 
absence of hard woody tissue in the centre of the cylinder, 
the closer correspondence is between Lep. Brownii and 
Tmesipteris, since in both the central tissue is thin-walled, 
while in P silo turn it is sclerenchymatous ; thus the histological 
characters noted in the plants above cited furnish us with 
a most interesting example of cross-correspondence. 
Finally, as regards the presence of a stellate, connected 
central xylem, there is a certain resemblance between our 
Lepidostrobus and, not only the Psilotaceae as above noted, 
but also with certain species of Lycopodium (L. Selago) 
and of Selaginella (S. spinosa ), and such examples serve to 
draw together the Lycopodinae on anatomical grounds, not- 
withstanding that in many species of these genera divergent 
arrangements appear to predominate. 
As it has already been shown elsewhere 1 2 that there are 
points of similarity between the sporangia of Lepidodendron 
and the sporangia of Tmesipteris , the close correspondence 
in respect of details of internal anatomy of the stem between 
Lepidostrobus Brownii and the Psilotaceae, as above demon- 
strated, becomes more specially interesting. 
1 loc. cit. Figs. 210-216. 
2 Proc. Roy. Soc., vols. 53 and 54; meetings of Feb. 16 and June 15, 1893. 
