266 



be doubted that it was present in the flora. A few years ago, 

 however, Mr. Willard Rusk was so fortunate as to find a fossil 

 Eqiiisetum at Station 13B, Florissant. Unfortunately the 

 sheaths were lost prior to preservation, but the fragment of a 

 fertile stem, showing two and a half joints, is sufficiently charac- 

 teristic for description. 



Equisetum florissantense n, sp. 



Fertile stem with joints extremely robust and short, 11.5 mm. 

 long and 13.5 mm. broad; a black or dark ring below articulation 

 of sheath; furrows close and numerous, 25 in lateral view, pre- 

 sumably 50 in all, the ridges minutely longitudinally striate, but 

 not tuberculate. 



Related to E. canaliculatum Knowlton, from the Yellowstone, 

 but apparently distinct by the short joints, which appear to be 

 mature. Among the living species it may be compared with 

 E. rohustum and E. hyemale. 



Fig. I. Equisetimi florissanteftse Cock.erell. 



Seward* remarks that "attempts to define strictly the specific 

 characters of fossil Equisetaceous stems must necessarily result 

 in provisional grouping as regards the majority of specimens, 

 which are too incomplete to furnish adequate taxonomic data." 

 The general type of Eqiiisetum, as described by Seward and 

 Lignier in numerous species as far back as the Jurassic, does not 

 seem to have undergone any marked modification up to the 

 present day. Competition with the modern flora has doubtless 



* Jurassic Plants from Chinese Dzungaria, Mem. Com. Geol. (Petrograd), 

 1911, p. 35. 



