THE INTERNAL STRUCTURE OF SIGILLAKIA ELEGANS. 547 
descendants except in the case of Szgillaria, the structure of whose cone shows some 
similarity with the fructification of Jswtes. Our other modern lycopods (Lycopodium 
and Selaginella) seem to have descended from the Carboniferous genus Lycopodites, 
with which they show much in common. 
The geological distribution of the Szgillaria whose structure is known also brings 
out an interesting point ; and though the evidence may not be sufficient for any definite 
conclusions, still it indicates changes which deserve recognition. 
The following table gives the age of the rocks which have yielded Sigillaria, showing 
their internal structure, and also indicates a few of the more prominent characters of the 
species discovered. 
TABLE. 
Lower Permian Sigillaria Menardi, | Stem without ribs Primary xylem a circle of 
Brongt. (Clathraria section) separate bundles. 
Secondary xylem forming a 
centrifugal zone. 
Do. Sigillaria spinulosa, | Stem without ribs Primary xylem a circle of 
Rost, sp. (Clathraria and Leio- separate bundles, some of 
(= Sigillaria Brardi, dermaria sections) which frequently coalesce. 
Brower) Secondary xylem forming a 
centrifugal zone. 
Upper Carboniferous No specimens show- 
Upper Coal Measures ing structure from 
this horizon 
Middle Coal Measures | Sigillaria elongata, | Stem ribbed Primary xylem in form of a 
(= “ Westphalian Brongt. (Rhytidolepis section) closed ring. 
partes”) Secondary xylem forming a 
centrifugal zone. 
Lower Coal Measures | Sigillaria elegans, | Stem ribbed Primary xylem in form of a 
Brongt. (Favularia section) closed ring. 
Secondary xylem forming a 
centrifugal zone. 
The non-ribbed Sigillariz are more characteristic of higher horizons and the ribbed 
Sigillariz of the lower horizons, but neither group is restricted to either series. 
The genus Sigillaria also extends into the Lower Carboniferous, where it is, however, 
very rare, but no specimens showing structure have yet been recognised from these 
rocks. In the following list I only mention the British species :— 
Lower Carboniferous. 
Carboniferous Limestone Series. 
Sigillaria Youngiana, Kidston : 2 Stem ribbed. 
Sigillaria Canobiana, Kidston ‘ ; Stem ribbed. 
Sigillaré h Stem without ribs. 
igillaria Taylori, Carr., sp. . ; : (Ulodendroid Clathraria.) 
Calciferous Sandstone Series. 
Sigillaria Taylori, Carr., sp. . | Oa ae 
(Ulodendroid Clathraria.) 
