I3 6 SCIENCE PROGRESS 



brief notices of those memoirs on the structure of British 

 Carboniferous plants which, for the most part, have appeared 

 since Scott's article was published. By arranging these memoirs 

 systematically it will be possible to give some idea of recent 

 contributions to our knowledge of each of the great groups of 

 Carboniferous plants. 



It will be apparent that the distribution of research has 

 been very uneven. The Lycopods, the Pteridosperms and the 

 Primofilices have received more attention than the Equisetales 

 or the Cordaitales, or to some extent the Sphenophyllales. This 

 may no doubt be accounted for, in part, by the chance which 

 has furnished fresh material for inquiry, but it is also partly 

 due to the fact that certain special advances have been made 

 within the last decade in regard to the first three groups above 

 mentioned, and thus an added stimulus has been given to re- 

 search in these directions. 



Equisetales 



This group has for some years past been comparatively 

 neglected. We still await a fuller knowledge of the structure of 

 the chief Lower Carboniferous representative, Archceocalamites, 

 derived from British material, and also of the interesting 

 Catamites petty airensis (48, p. 157) in which centripetal xylem is 

 found to occur. 



As regards the Upper Carboniferous members, the re- 

 description by Hickling (22) of the rare Calamite cone, 

 Palceostachya vera, is of great interest, especially as throwing 

 light on the homologies of the corresponding organs of Calamo- 

 stachys, and on the question of the general relationships 

 of the Equisetales to the Sphenophyllales. Hickling finds that 

 Palceostachya is more closely connected with Catamostachys 

 than has hitherto been supposed, and that the axillary position 

 of the sporangiophore in the former is derived from the condition 

 of affairs met with in the latter genus. 



The " relation of root to stem " in the genus Catamites has 

 been discussed by Maslen (38). The roots prove to be mainly 

 adventitious and not to be borne in the same manner as in the 

 recent Equisetitm. There is no evidence of any connection 

 between the roots and the infra-nodal organs of Williamson. 

 These infra-nodal organs were the subject of an earlier inquiry 



