336 STUDIES IN FOSSIL BOTANY 



fructification, where known) that their association in a 

 single family is fully justified. 



We have still to consider a genus which at present 

 stands a little apart from the rest of the family. 



5. Stauropteris. — The best - known species, 5. 

 oldliamia, Binney, is one of the commonest fossils of 

 the Coal-measure nodules ; a very similar species, of 

 Lower Carboniferous age, has recently been named 

 S. burntislandica by M. Paul Bertrand. We will 

 confine our attention to the former. 



The stem is unknown ; the specimens consist of 

 fragments of the petiole and rachis of a highly com- 

 pound frond, without any recognisable lamina, but 

 bearing sporangia on its ultimate branches. In the 

 large petioles the xylem has a characteristic cruciform 

 section, while the whole stele is approximately square, 

 the phloem filling up the bays between the xylem-arms, 

 and sometimes extending to the centre, so as to 

 interrupt the continuity of the wood (Fig. 1 26). The 

 example figured is tetrarch ; often, however, there is 

 more than one protoxylem-group at each angle, though 

 this condition may be correlated with the branching. 

 As M. P. Bertrand has observed, the protoxylem is 

 sunk a little below the surface of the wood, which is 

 therefore not strictly exarch. The phloem contains 

 large sieve-tubes, and the sieve-plates on their lateral 

 walls are sometimes clearly shown. A lax, palisade- 

 like tissue occurs below the epidermis, and probably 

 had the function of assimilation. The branches were 

 given off in pairs, successive pairs springing from 

 opposite sides of the rachis, a mode of branching 



