35i 
of Lepidostrobus Brownii , Schpr. 
the sections of Brown’s cone, but at least it is present in 
closely allied plants. All these considerations serve to draw 
the Lycopodinous plants of the present and the past more 
closely together as a natural family, while it is interesting to 
note that the lines of similarity as regards structure, form, 
heterospory and details of sporangia, do not focus themselves 
specially between any two genera, but are such as to suggest 
complex cross-relationship between the several representatives 
of this very natural series. 
When we pass from the vascular tissues to the study of the 
sporangia of these several forms, differences are to be noted. 
I have shown elsewhere 1 that there is considerable variety in 
form and complexity of the sporangium within the genus 
Lycopodium ; but, while more or less extended and curved 
in a plane tangential to the axis, the sporangium does not in 
any case extend far along the leaf in a radial direction from 
the axis. The sporangium of Lepidodendron , however, differs 
in not being strongly curved in the tangential plane, while it 
is extended largely in a radial direction ; trabeculae of sterile 
tissue have been found rising from the base of the sporangial 
cavity and extending far up into the sporogenous mass. 
There can be no doubt of the homology of the sporangium 
of Lepidodendron with that of Lycopodium. But when the 
sporangium of Lepidostrobus Brownii is compared with that of 
Tmesipteris or P silo turn a question of the homology may arise. 
On grounds of internal development of the synangia in 
Psilotum and Tmesipteris , which are stated elsewhere 2 , I was 
led to agree with the conclusion of Graf Solms from external 
observation of development in Psilotum , viz. that the wliole 
sporangiophore is of foliar nature, and that the synangium is 
a growth from its upper surface. There is also a general 
similarity in form between the synangium of Tmesipteris and 
the sporangium of Lepidostrobus. Thus the whole synangium 
of Tmesipteris would correspond in position and form to the 
sporangium of Lepidostrobus , that is, a body with two or three 
1 Proc. Roy. Soc., no. 304, vol. 50, p. 267, &c., 1892. 
2 Proc. Roy. Soc., no. 321, vol. 53, p. 19, r893. 
