. Fossil plants : for students of botany and geology . Paleobotany. xxxvn] 451 of Cycadeoidea. The strobilus was probably borne at the apex of a lateral branch given off from a stem covered with persistent petiole-bases: there is no evidence that this was the case, but the appearance of the ovoid cone suggests comparison with those of Williamsonia gigas which were terminal on fairly long branches and not partially hidden among the bases of fronds as in Cyca- deoidea. It is, however, possible that the cone of Williamsonia scotica is a lateral structure: this suggestion is based o
. Fossil plants : for students of botany and geology . Paleobotany. xxxvn] 451 of Cycadeoidea. The strobilus was probably borne at the apex of a lateral branch given off from a stem covered with persistent petiole-bases: there is no evidence that this was the case, but the appearance of the ovoid cone suggests comparison with those of Williamsonia gigas which were terminal on fairly long branches and not partially hidden among the bases of fronds as in Cyca- deoidea. It is, however, possible that the cone of Williamsonia scotica is a lateral structure: this suggestion is based on the occur- rence of a small branch or bud, which may be the apex of the whole fertile shoot, given off from the cone-axis but only revealed. Fig. 562. Williamaonia scotica. Transverse section; S, scales and megasporo- phylls; u, bract showing detached superficial tissue on the inner side. {ca. x 2.) in transverse sections. The interseminal scales, 2 mm. long and 0-23 mm. broad at the truncate distal end (fig. 563), are polygonal in section and arranged as rosettes of 5—6 around each megasporo- phyll (fig. 564, a section tangential to the peripheral layer of scales and sporophyUs). The megasporophylls, equal in length to the scales, consist of a cyhndrical axis bearing a terminal megasporangium, an undifferentiated nucellus, enclosed in a single integument prolonged as a micropylar tube above the conical end of the nucellus (fig. 563, B, C, a). Fig. 562 represents a transverse section through the cone showing the cyhndrical axis with its compact covering layer (fig. 563, A, s) of sterile and fertile appendages, and beyond this sections of the enveloping bracts embedded in a dense felt of long hairs. The tissue of the axis, though very imperfectly preserved, shows occasional groups 29—2. 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 perfect
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishercambr, bookyear1898
