CLASSIFICATION OF CALAMARIEAE 79 



not seem to be good enough to settle the point for 

 certain. 



It appears that the stems with the structure of 

 Calamodendron had much longer internodes than those 

 of the Arthropitys type, and that the branches were 

 scattered irregularly, and not limited to certain definite 

 nodes as in the Arthropitys group. These and other 

 differences are said to render the casts of Calamoden- 

 dron recognisable ; they correspond to the Stylocalamites 

 of Weiss's system. In Calamodendron, as in the former 

 group, the upright stems sprang from subterranean or 

 aquatic rhizomes. Grand'Eury believes that the develop- 

 ment of the secondary wood, in Calamarian stems of 

 the same type, increases as we ascend from the lower to 

 the higher horizons of the Coal-measures. 



In addition to the three groups just enumerated, we 

 have the ancient genus Bornia or Archaeocalamites, 

 with its forked leaves and fructifications of a somewhat 

 Equisetiform character. There is another genus which 

 Grand'Eury has distinguished under the name of Auto- 

 phyllites; its fructifications are much like those attributed 

 to Bornia, and it had large dichotomous leaves. The 

 plant is of Upper Coal-measure age. 



It is important to point out how nearly some of 

 the Calamarieae of the Carboniferous period approached 

 our living Equisetum. In some, as we have seen, the 

 fructification was of a very similar type, and there is 

 no longer any doubt that many members of the family 

 had leaves coherent at the base, so as to form a regular 

 sheath (see Fig. 12). It is probable, as already 

 mentioned, that the sheath may often have become 

 split, as the stem within grew in thickness, and that 



