CALAMARIEAE. 295 



are linear and not united laterally into a sheath, and will have to be de- 

 scribed in greater detail in the sequel. In addition to the leaves large 

 patelliform scars, the points of attachment of lateral branches, are found 

 at the nodes with a different arrangement and distribution in each case. 

 In many instances entire branch-systems have been found in connection, 

 and in this way it has been ascertained that the branches often narrow 

 and become conical at the base, as in Equisetitae. Impressions also of 

 adventitious roots have not unfrequently been seen connected with the 

 stems which produce them. 



There are virtually three different states of preservation in which 

 these Calamitae are presented to our notice. They appear most com- 

 monly as cylindrical or flattened casts, presenting the form of a broad 

 inner medullary cylinder, and analogous with the calamitoid casts of 

 Equisetitae. They appear also in the form of surface-impressions with 

 the leaf-scars, to which in extremely rare cases the leaves are still attached. 

 Such surface-pictures occur more especially on the rind of coal on the 

 casts, where that is well preserved ; but it is true that this is not often the 

 case in our collections. Lastly, they are found in a state of petrifaction, 

 and then usually without the rind, and containing only the vascular bundle- 

 system or xylem-system which incloses the medullary cavity. Silicified 

 specimens of this kind occur especially at Autun, Grand' Croix and Chemnitz, 

 and are a generally distributed portion of the material contained in the 

 calcareous nodules of England and Westphalia. It is remarkable that 

 almost all the many petrified specimens which have been examined show 

 the presence of a considerable mass of secondary wood traversed by primary 

 and secondary rays. 



Further, undoubted impressions of Calamitae have been repeatedly 

 found in immediate connection with well-characterised spike-like fructi- 

 fications, which are also of frequent occurrence under other circumstances ; 

 these fructifications present the characters of those of archegoniate plants, 

 sometimes even allowing spores of two kinds to be seen, and in most cases 

 recall mutatis mutandis even at first sight the conditions observed in Equi- 

 setum. 



On the facts thus briefly enumerated, and which must be examined 

 more carefully later on, are founded the views which prevail among the 

 different authors respecting the systematic position of Calamarieae. We 

 must here give a preliminary account of these views, in order to make 

 our further remarks intelligible. 



The question seemed to the older authors to be extremely simple, 

 so long as the petrified specimens were either not known or little regarded. 

 The stems and the fructifications just mentioned were considered to belong 

 to one another, and thus was formed the family of Calamarieae, which 

 appeared to stand in the very closest relationship to Equisetae. Afterwards 



