. Fossil plants : for students of botany and geology . Paleobotany. 414 BENNETTITALES [CH. no evidence of the presence of any reproductive organs. A similar bud is described by Lignier^ in the stem of C. micromyela. The absence of lateral flowers is, however, hardly a sufficient reason for separating this stem generically from other species of Cyca- deoidea: negative evidence in this case is of doubtful value. While it is possible that the strobih were terminal as in most recent Cycads, it is more probable that they were lateral. The surface-features, though not perfect, are for the most part
. Fossil plants : for students of botany and geology . Paleobotany. 414 BENNETTITALES [CH. no evidence of the presence of any reproductive organs. A similar bud is described by Lignier^ in the stem of C. micromyela. The absence of lateral flowers is, however, hardly a sufficient reason for separating this stem generically from other species of Cyca- deoidea: negative evidence in this case is of doubtful value. While it is possible that the strobih were terminal as in most recent Cycads, it is more probable that they were lateral. The surface-features, though not perfect, are for the most part sufficiently well preserved to enable one to recognise the bract- encircled axes of strobih were any present. If as Wieland beUeves, and he is probably correct, the production of flowers was the culminating event in the hfe of these Cycadean plants, the absence of fertile shoots is merely an expression of immaturity. It is,. Fig. Cycadeoidea gigantea. Transverse section of the stem. however, difficult to understand how lateral branches could find their way to the surface among the crowded and cork-covered leaf-bases of the stem. The absence of flowers may be due to some \infavourable external conditions. The petioles consist of parenchymatous ground-tissue with many secretory sacs and in some cases twelve partially preserved vascular bundles: the xylem consists of radial rows of centrifugal tracheids and medul- lary rays, but it is not possible to say whether any centripetal xylem was present. A fairly thick band of phelloderm and periderm, apparently subepidermal in origin, forms the peripheral tissue, and in places epidermal cells with attached ramenta are clearly preserved. The ramenta are of the type characteristic of the majority of fossil Cycadean stems. Stomata were found showing a pair of guard-cells and apparently two subsidiary cells: the epidermal cells have straight walls. 1 Lignier (01).. Please note that these images are extracted from scanned page images th
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishercambr, bookyear1898
