. Studies in fossil botany . Paleobotany. ROOTS OF CALAMARIEAE 45 cases, to trace the centripetal strands of xylem in a young root, and to find, alternating with them, groups of delicate tissue, which could only be interpreted as primary phloem. Hence, in this respect also, the structure proves to be that of a typical root. We further found that the bases of branches of Astromyelon are surrounded by a distinct cortex of their own, as they traverse the outer tissues of the parent organ. Hence they must have been endo- genous in origin, thus agreeing with rootlets. Another important point is the
. Studies in fossil botany . Paleobotany. ROOTS OF CALAMARIEAE 45 cases, to trace the centripetal strands of xylem in a young root, and to find, alternating with them, groups of delicate tissue, which could only be interpreted as primary phloem. Hence, in this respect also, the structure proves to be that of a typical root. We further found that the bases of branches of Astromyelon are surrounded by a distinct cortex of their own, as they traverse the outer tissues of the parent organ. Hence they must have been endo- genous in origin, thus agreeing with rootlets. Another important point is the entire absence of anything like nodes. There is thus, on the whole of the evi- dence, no room for doubt that the old genus " Astromyelon " simply represents the roots and rootlets of Cata- mites} Other allied forms appear to stand in a similar relation to Archaeocalamites and Calamodendron. The endodermis was evidently double, as in the roots of recent Horsetails ; this is well shown in the small tetrarch rootlet represented in Fig. 16. The large intercellular spaces of the cortex were no doubt an adaptation for growth under water, or in wet mud. 1 Williamson and Scott, "Further Observations, etc.," Part ii. The Roots of Catamites, Phil. Trans, vol. 186, B, Fig. 16.—Catamites, sp. Transverse section 01 small tetrarch rootlet, showing wood (x), with slight secondary growth, double endodermis, lacunar cortex (c), and thickened exodermis. X 25. From a photog'aph. Phil. Trans. W. and S. Will. Coll. 1S90, 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
Size: 1570px × 1591px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherlondonaandcblack
