336 Bower . — On the Structure of the Axis 
be seen in sections traversing the endodermis of living plants, 
owing to the brittleness of the walls of that tissue. The above 
characters point to the conclusion that the sheath in question 
is an endodermis, though it is to be noted that it is not always 
so recognizable as in the part of the section selected for our 
Fig. 3 A. Clearly this endodermis will correspond in position 
to the innermost layer of the cortex, distinguished by M. Hove- 
lacque as the ‘ Gaine ’ 1 . He did not, however, recognize any 
marking on the radial walls of the cells 2 . The tissue lying 
outside this endodermis is the inner dense band of the cortex, 
consisting of parenchyma, with sclerenchymatous elements, 
which may be scattered singly, or, as the outer parts are 
reached, they may preponderate, and form a dense mass of 
tissue (Fig. 7), in which the bundles of the leaf-trace are 
embedded. Returning to the tissue which lies between the 
ring of wood and the endodermis, the characters appear to be 
ill-defined — the band of tissue is of variable thickness, being 
sometimes reduced to but two layers (Fig. 3 A, opposite the 
projecting tooth), or it may increase to four or more. I have 
not been able to recognize any characters distinctive of soft 
bast beyond the delicate cell-walls, and in any case, if a true 
phloem was present, it can have existed only in comparatively 
small quantity. There is, however, nothing to preclude the 
idea that this tissue represented the phloem, such as it was. 
A comparison of this central stele with that in other 
Lycopodinae shows that it is most nearly matched by that 
in the Psilotaceae. With most species of Selaginella the cor- 
respondence is not close : apart from the peculiar character 
of the endodermis in that genus, the vascular arrangement 
is quite distinct in most species ; in the larger species, 
however, such as 5 . Willde 7 iovii i where three large vascular 
bundles are seen in the transverse section, these show at 
times a crenulated margin : but the nearest resemblance is 
naturally to be expected in the sub-genus Selaginella proper, 
with multifarious leaves, such as Selaginella spinosa , P. B. ; 
1 loc. cit. Figs. 11, 12 (g, g). 
2 loc. cit. p. 148. 
