344 Bower . — On the Structure of the Axis 
also secondary tissues ; what we have before us is the primary 
condition of the cortex, for purposes of comparison with 
living forms in which, as in Lepidostrobus Brownii , no 
secondary changes appear. In Solms’ Fig. 23 of Lepi- 
dodendron selaginoides the dark zone of firm tissue, outside 
the vascular cylinder, but internal to the lax tissue which 
he describes as the ‘ inner cylinder/ corresponds to what 
I have described as the inner cortex . A similar firm band 
of cortical tissue surrounds the vascular stele in certain 
species of living Lycopods. The lax tissue, which in 
Lepidostrobus Brownii I have called the middle cortex , 
corresponds to the imperfectly preserved tissue, which Solms 
styles the ‘ inner cylinder/ while the dense and broad outer 
cortex of Lep. Brozvnii corresponds to the inner part of that 
broad band which Solms termed the middle rind, together 
with what remains of primary cortex outside the zone of 
thickening. It is unfortunate that this difference of terms 
should exist ; it is due to the fact that while I have kept 
in view the primary condition of the cortex, and its dif- 
ferentiation in living Lycopods, Solms has based his terms 
upon fossils which show the results of secondary change. 
That the latter is unsatisfactory seems to me sufficiently 
plain from the fact that the ‘ middle rind ’ of Solms includes 
both primary and secondary tissues, while no account is 
taken by him of the innermost firm band of cortex. But, 
whatever be the terminology, the three bands of Lep. Brownii 
find their counterparts in the cortex of Lep. selaginoides ; 
the correspondence is more evident on comparison of the 
larger and more detailed drawing of Williamson *, and from 
this, other points of similarity may be traced, which are 
necessarily omitted in Solms’ smaller-scale drawing. The 
inner firm band of cortex is also shown by Williamson in 
longitudinal section 2 . 
I have examined several specimens of Lep. selaginoides 
in my possession, and find the firmer band surrounding the 
1 Phil. Trans. 1881, PI. 48, Fig. 4. 
2 Phil. Trans. 1878, PI. 22, Fig. 34, g. g. 
