204 kidston: tiik kloka of thk cauhoxifekous period. 



Macroiitdchija Scliiniper is anotlier genus of Calamitic cones. 

 These attained to considerable size, and are much larger and 

 broader than those of the three preceding genera. The cones are 

 composed of alternating closely placed verticils of many bracts, 

 united to each other tlirougliout the greater portion of their 

 length ; only the short upturned extremities of the bracts remain 

 free. Each whorl of bracts thus forms a saucer-like collar which 

 surrounds the thick axis of the cone. The an-angement of the 

 sporangiophores has not been clearly made out. 



Other types of Calamitic cones are known, but those mentioned 

 are the principal forms which occur in British Carboniferous rocks. 



Occasionally specimens of Calamites are found showing the 

 remains of their rootlets. These are — in whole or in part — the 

 fossils for which Lindley and Hutton founded the genus Pinnularia 

 (Plate XXXV., fig. 1 — Pinnularia columnaris). They consist of 

 roots pinnately giving off lateral roots, which in turn bear the 

 rootlets, apparently in the same plane. 



That the Calamariece and Equisetacece are closely related is 

 beyond all doubt, and there seems to be no satisfactory reason why 

 they should not be united in one family under either of these 

 names, preferably under that first mentioned. 



The genus Calamites seems to have entirely disappeared with- 

 out leaving any modern representative, while the less important 

 palaeozoic genus Equisetites is probably the ancestor of the recent 

 Eq7iisetum. 



