70 STUDIES IN FOSSIL BOTANY 



morphology or affinities of Cingularia. We cannot be 

 absolutely certain of the accuracy of our interpretations, 

 and still less can we be certain whether we have to 

 do with a Calamarian or a Sphenophyllaceous plant. 

 These questions can only be cleared up if specimens 

 with the structure preserved should be discovered. 



5. Archaeocalamites. — A fourth type of Calamarian 

 fructification remains to be noticed. This is a simple 

 one to describe, because it has much in common with 

 that of the only surviving genus of Equisetales, the 

 recent Equisetum. The remarkable genus Archaeo- 

 calamites, characteristic of the oldest Carboniferous 

 'strata and of the Upper Devonian, appears, according 

 to M. Renault's observations, to have borne the fructifi- 

 cation of which a fragment is represented in Fig. 

 24, B. The cones occur associated with the stems and 

 dichotomous leaves of that genus, though the evidence 

 from actual continuity is wanting. The cone bears 

 whorls of sporangiophores, from eight to ten in each 

 whorl ; they have the usual peltate form, with the 

 expanded portion little developed, and each appears to 

 have borne four sporangia. Sterile bracts are not 

 shown, but it is quite probable that they may have 

 occurred in scattered whorls, at long intervals, as was 

 clearly the case in the genus Pothocites, associated 

 with Archaeocalamites in the Lower Carboniferous of 

 Scotland. Pothocites consists of large cylindrical 

 strobili, constricted at intervals, the constrictions no 

 doubt marking the position of the sterile whorls. 1 The 



1 See Kidston, "Affinities of the Genus Pothocites," Trans. Bot. Soc. 

 Edinburgh, 1883. 



