316 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



comparison, the Pseudoborniales in habit and structure, in so far as 

 these are known, were evidently allied to the Protocalamariaceae 

 (formerly referred to the genus Bornia) and help to bridge the gap 

 between the Calamariae and the Sphenophyllae. 



The Protocalamariaceae, which are common in the Devonian and 

 Lower Carboniferous, occurring as late as the Pottsville formation 

 of the Upper Carboniferous, are generally referred to the genus 

 Archaeocalamites, although the terms Bornia, Protocalamites, Astero- 

 calamites, etc., have also been used for them. The steins, most fre- 

 quently preserved as casts, were often of considerable size; they 

 show low, fiat, nonalternating ribs separated by shallow furrows ; the 

 internodes were of unequal lengths and the lateral branches were 

 irregularly grouped at some and not at other nodes. The leaves 

 were free and in whorls; they were narrow and lanceolate or re- 

 peatedly dichotomous with linear or filiform segments. According 

 to Renault the pith cavity was large and surrounded by a woody 

 cylinder of wedge-shaped groups of tracheitis with secondary rays. 

 A carinal canal was located at the apex of each primary group and 

 the primary rays were shut off by interfascicular wood early in the 

 course of secondary thickening. In a stem from the basal Carbo- 

 niferous of Scotland a considerable arc of centripetal wood was 

 formed inside the carinal canal — a primitive feature, otherwise un- 

 known in the Calamariales except in the roots. 



Such incomplete accounts as are available indicate that the cones 

 may have exhibited variations comparable with those among the 

 Sphenophyllae, although much less is known regarding the former. 

 In the cones described by Renault there were no sterile bracts and each 

 sporangiophore bore four sporangia, while in other cones (Pothocites) 

 sterile bracts appear to have been more or less developed. The leaves 

 suggest the Pseucloborniales and some of the Sphenophyllae ; the stele 

 was like that of a calamite, while the absence of sterile bracts in some 

 of the cones suggests the Equisetales. There can be no doubt but that 

 the Protocalamariaceae represent a more synthetic group than the 

 Calamariaceae, although probably ancestral to them and to the 

 Equisetales also. 



The family Calamariaceae was one of the dominant groups of plants 

 during the Carboniferous and various of its members often reached 

 a large size with a corresponding complexity of structure. Pith casts 

 upward of 30 feet in length and 12 inches in diameter have been 

 recorded, and Grand 'Eury estimated the height of some of the French 

 calamites as about 100 feet and with a trunk diameter of several feet. 

 Secondary wood was usually formed, although the common mode of 

 preservation was as casts of the fistular medullary cavity. The 

 vascular bundles usually alternated at the nodes. The foliage of the 

 Carboniferous forms comprised two main types — namely, Asterophyl- 



