THE CAEBOXIFEROrS FLORA. 169 



and narrow furrows, and undulated in » remarkable manner even 

 when the stems are flattened. This undulation is, however, perhaps an 

 indication of vertical pressure while the plant was living, as it seems 

 to have had an unusually thin and feeble cortical layer, and the un- 

 dulations are apparently best developed in the lower part of the stem. 

 M the nodes the ribs are often narrowed and gathered together, 

 especially in the vicinity of the rounded radiating marks which ap- 

 pear to indicate the points of insertion of the branches. At the top 

 of each rib we have the usnal rounded aieole, probably markiag the 

 insertion of a prinuury branchlec 



The branches have slender ribs and distant nodes, from which 

 spring secondary branchlets in whorls, these bearing in turn small 

 whorls of acicular leaflets much curved upward, and which are ap- 

 parently round in cross section and delicately striate. They are 

 much shorter than the leaves of Calamites Suekorii, and are less 

 dense and less curved than those of C. twdosus, which I believe to be 

 the two most closely allied species. 



'Lesquereux notices this species as characteristic of the lower part 

 of Hhe Carboniferous in A rkansas. 



It will be observed that I regard the striated and ribbed stems not 

 as internal axes, but as representing the outer surface of the plants. 

 This was certainly the case with the present species and with C. 

 Suckovii and C. nodosus. Other species, and especially those which 

 belonged to Calamodendron, no doubt had a smooth or irregularly 

 wrinkled external bark ; but this g^ves no good ground for the man- 

 ner in which some writers on this subject confound Calamites with 

 Calamodendra, and both with Ast^ophyllites and Sphenophyllum. 

 With this no one who has studied these plants, rooted in their native 

 soils, and with their appendages still attached, can for a moment 

 sympathise. One of the earliest geological studies of the writer was 

 a bed of these erect Calamites, which he showed to Sir C. Lyell in 

 1841, and described in the " Proceedings of the Geological Society " 

 in 1851, illostrating the habit of growth as actually seen well ex- 

 p(»ed in a sandstone cliff. Abnndant opportunities of verifying 

 Hie condnaons formed at tliat time have since occurred, the results 

 of which have been summed up in the figures in Acadian Geology, 

 whidi, though they have been treated by some botanists as merely 

 restorations, are in reality representations of facts actually observed. 

 On these subjects, without entwing into details, and referring 

 for these to the elaborate discussions of Schimper, VTilliamson, and 

 HcNab, and to my paper on the sul^ect, " Journal of ihe Geological 

 Sodety," voL xxvii, p. 54, 1 may remark : 



