. Studies in fossil botany . Paleobotany. PROTOCALAMITES 37 is interesting that this Lower Carboniferous species should be the only Calamite so far observed which has centripetal wood. The protoxylem is in the usual position, in or adjacent to the "carinal" canal, but in this case the development of the primary xylem pro- ceeded in both the inward and outward directions, for each bundle possesses a considerable arc of centripetal. \ / se ( Fig. 11.—Cakinritcs (Protocalainitcs)pettycuroisis. Transverse section of the xylem of a vascular bundle in the stem. _/i, fascicular canal ; .r-,
. Studies in fossil botany . Paleobotany. PROTOCALAMITES 37 is interesting that this Lower Carboniferous species should be the only Calamite so far observed which has centripetal wood. The protoxylem is in the usual position, in or adjacent to the "carinal" canal, but in this case the development of the primary xylem pro- ceeded in both the inward and outward directions, for each bundle possesses a considerable arc of centripetal. \ / se ( Fig. 11.—Cakinritcs (Protocalainitcs)pettycuroisis. Transverse section of the xylem of a vascular bundle in the stem. _/i, fascicular canal ; .r-, secondary wood ; xi, centripetal wood, on the inner side of the canal. X about 140. S. Cull. 1104. (G. T. G.) wood on the side of the canal towards the pith (Fig. i I, xi). Dr. Lotsy has suggested to me that a new genus or subgenus, Protocalamitcs, should be founded on this form, and the proposal may be provisionally adopted, but it is possible that when the course of the bundles has been traced the species may prove to belong to Archaeocalamites (p. 70). The significance of the centripetal xylem as a character shared with other. 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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