. Studies in fossil botany . Paleobotany. THE STEM OF CALAMITES 23 transverse section of a stem, the canals are not perfectly empty, but that they contain minute rings adhering to their edges, as indicated in Fig. 4. This suggests very strongly the position of the annular and spiral tracheides fix sc. in Equisetum, which are often found within the carinal canal. To determine the true state of the case, however, a very detailed examination was necessary. There are now many sec- tions showing these canals quite clearly, and proving that they contain the first- formed woody elements, or protoxyle
. Studies in fossil botany . Paleobotany. THE STEM OF CALAMITES 23 transverse section of a stem, the canals are not perfectly empty, but that they contain minute rings adhering to their edges, as indicated in Fig. 4. This suggests very strongly the position of the annular and spiral tracheides fix sc. in Equisetum, which are often found within the carinal canal. To determine the true state of the case, however, a very detailed examination was necessary. There are now many sec- tions showing these canals quite clearly, and proving that they contain the first- formed woody elements, or protoxylem, of the vascular bundles. Fig. 6 represents a radial section passing through the canal of one of the bundles. On the inner side of the canal is pith ; on the outer side wood. We notice that the canal is to a great extent occupied by the disorganised tracheae. It is a point of some importance that the disorganisation is found to be greatest on the inner side of the canal, while, as we approach its outer edge, the tracheae become more continuous. We know that the disorganisation of the tracheae is constantly greatest in that part of the primary wood which is differentiated before the growth in length is completed. Hence wc may infer that the. Sc Fig. 6.—Catamites, sp. Part of radial section through primary wood. J>x, disorganised spiral and annular tracheides in the canal ; sc, scalari- form tracheides of the more external primary wood. On the left is the pith. X about 160. Phil. Trans. W. and S. Will. Coll. 20 Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Scott, Dukinfield Henry, 1854-1934. London, A. and C. Black
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