. Bulletin of the British Museum (Natural History), Geology. Figs. 5, 6. Fig. 5, Transverse section of part of the stem stele near its apex showing the incompletely differentiated metaxylem and an isolated mesarch protoxylem tracheid. () Oliver Coll. 1247. x 80. Fig. 6, A small group of dark sclerized cells from the inner cortex of the stem. Gordon Coll., King's College, x Fig. 7. Hairs from the stem and the base of the petiole, a-d, Kidston Coll., Glasgow University, slide 549c ; e-g, Hemingway Coll., () No. (sections 35, 52 and 98 respectively). All X 135 appro
. Bulletin of the British Museum (Natural History), Geology. Figs. 5, 6. Fig. 5, Transverse section of part of the stem stele near its apex showing the incompletely differentiated metaxylem and an isolated mesarch protoxylem tracheid. () Oliver Coll. 1247. x 80. Fig. 6, A small group of dark sclerized cells from the inner cortex of the stem. Gordon Coll., King's College, x Fig. 7. Hairs from the stem and the base of the petiole, a-d, Kidston Coll., Glasgow University, slide 549c ; e-g, Hemingway Coll., () No. (sections 35, 52 and 98 respectively). All X 135 approx. The Petiole As has been stated already, the petioles arise from the stems in a close spiral and usually show an approximately two-fifths divergence (Text-figs. 1-4). In the great majority of specimens the xylem and cortex are the only tissues preserved and even these may show some degree of breakdown. In the case of the xylem the protoxylem is the only part affected but the cortical tissues may become disorganized and, partly or almost wholly, be replaced by aggregates of calcite. These have crushed and ruptured the cortical cells and produced a pseudo-cellular structure in which the sphaerules of calcite have become surrounded by the broken down cell remnants (PI. 57, fig. 6). This condition is not uncommon in petrified plant remains from Burntisland and was noted and figured by Gordon in some of the specimens of Diplolabis examined by him (Gordon, 1911). The protoxylem of the petiole trace is initially mesarch with a single protoxylem. 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 British Museum (Natural History). London : BM(NH)
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