DAWSON — SIGILLARIA, CALAMIIE3, AlfD CALAMODENBROIJ. 155 



the name Calamopitus* for a group believed to be intermediate be- 

 tween Calamoclendron and true Calamites. On still other grounds, 

 Bornia and other genera or subgenera have been separated from Cala- 

 mites proper. Latterly Schimper has endeavoured to combine the view 

 of the Equisetaceous affinities and annual growth of the stems of 

 Calamites with what, at first sight, seems the totally irreconcilable 

 woody character of the stem of Calainodendron as described by 

 Cotta, Dawes, and Binney. 



In all my own publications on this subject, from the date of my 

 first paper on Calamites pubHshed in the Journal of this Society f, I 

 have held that Calamites proper are Equisetaceous plants, having 

 the external characters of their stems preserved, and that in the last 

 respect they differ from the internal casts which belong to Calamo- 

 dendron. All my subsequent observations have served to confirm 

 these conclusions, which I would now illustrate by the following 

 considerations. 



1. The true Calamites (e. g. C. Sackovii, C. cannceformis, C. Cistii, 

 &c.), when well preserved, present, externally, somewhat flat smooth 

 striated ribs, with distinct nodes, and having, at the upper end of 

 each rib, a rounded areole with a central dot or scar, marking the 

 disarticulation of a leaf, branchlet, or root, or, in some cases, the ex- 

 tremity of one of those radial prolongations of the pith which have 

 been described by "Williamson. In one specimen in my possession 

 there is a double set of marks — smaller ones on the node, apparently 

 belonging to the appendages, and larger marks below the node, which 

 may represent the radial prolongations of the pith (PL X. fig. 22). The 

 cortical investment is very thin and dense, and presents externally 

 the characters of an epidermis, not shoAving, as in the case of Stern- 

 hergia or Calamodendron, a coating of woody fibres externally, and 

 therefore cannot be regarded as a mere medullary sheath or, as 

 Schimper supposes, the membrane lining the hoUow interior of the 

 stem. I may remark here, that erect Calamites are sometimes sur- 

 rounded by a calcareous or ferruginous concretionary coating which 

 must not be confounded with the true surface of the stem. 



2. The ordinary Calamites are seen to stand erect, rooted in situ, 

 and attached together at the bases, or arising from rhizomata. The 

 stems can be seen to bud from each other ; and the roots can be 

 traced proceeding from their bases and lower nodes. Pigures of erect 

 specimens were given in my paper on Erect Calamites, and also in 

 that on the South Jogginst. Abundant specimens may be obtained 

 in the magnificent petrified Calamite brakes at the last-mentioned 

 locality, and, I venture to say, cannot be studied by any geologist 

 without producing the conviction that the erect cylindrical casts im- 

 bedded in groups in the sandstone must represent the true external 

 form of the plant. I have also shown, in the paper above cited, that 

 these erect stems are crushed by lateral pressure, and broken down 



* Preoccupied by linger for certain Devonian plants. 



t On the Occurrence of Upright Calamites near Pictou, Nova Scotia, Quart. 

 Journ. Geol. Soc. vol. vii. p. 194. 



X Quart. Journ. Creol. Soc. yol. vii, p. 194, and vol. s. p. 1. 



