340 Bower,— On the Structure of the Axis 
the concentric type. The question has been discussed by 
Solms 1 as to the type of bundle of the leaf-trace in Lepido- 
de 7 idron , and has been left open, owing to the insufficiency 
of evidence : in the case of L. Williamsoni , to which species 
our fossil appears to correspond in its general characters, the 
evidence is in favour of the collateral type 2 . The remarkably 
well-preserved bundle shown in our Fig. 4 A seems to me 
to show clearly, as regards L . Brownii , that the bundle 
of the leaf-trace was of the collateral type ; it is to be noted, 
however, that this character does not come out so clearly 
in all the leaf-trace bundles of this cone (compare Fig. 4 B). 
The results of M. Hovelacque as regards the structure 
of the leaf-trace bundles in Lep. selaginoides are interesting 
for comparison 3 : he finds the bundles to be of the collateral 
type, more distinctly so than in Lep . Harcourtii\ the size 
of the bundle varies on its course outwards, being largest 
in the middle cortex. He describes the bundle as being 
surrounded by a sheath, but this is not clearly defined. In 
these broad characters there is a general correspondence with 
the results above described for Lepidostrobus Brownii , but 
the variations of structure illustrated in Figs. 4, A and B , 
make it difficult to draw detailed comparison. 
Of a number of species of Lycopodium which have been 
examined for purposes of comparison, L . Phlegmaria , one 
of the large-leaved species, showed the nearest correspondence 
of structure of the leaf-trace of our Lepidostrobus ; a section 
is shown in Fig. 4 C\ the very small proportion of tissue 
referable to the phloem is a remarkable feature, while the 
number of cells which have divided by walls parallel to 
the limit of the bundle (marked x) is to be noted for purposes 
of comparison with the Lepidostrobus . 
A comparison of transverse sections of the leaf-trace of 
Tmesipteris shows correspondence of structure quite as close 
as this ; as examples, the Figs. 217, 218, 231 of M. Bertrand 4 
1 Fossil Botany, Engl, ed., pp. 219, 226. 2 loc. cit. p. 226. 
3 loc. cit. Figs. 20-37 and PP- 1 50-15 2. 
4 Arch. Bot. d. Nord de la France, Vol. i, p. 500, &c. 
