. Studies in fossil botany . Paleobotany. CALAMOSTACHYS 55 the fourfold division, so general in spore mother-cells, already prevailed among these Palaeozoic plants. In many cases the spores of the same tetrad are very unequally developed, some remaining quite small (Fig. 22, B and C); we may regard the latter as abortive spores, their suppression having allowed of the better nutrition of their surviving sister-cells. The mature spores show a triradiate marking on one side, probably lmL_. Fig. 21.—Calamostachys Binneyana. Part of tangential section of cone, showing portions of two whorls of bra
. Studies in fossil botany . Paleobotany. CALAMOSTACHYS 55 the fourfold division, so general in spore mother-cells, already prevailed among these Palaeozoic plants. In many cases the spores of the same tetrad are very unequally developed, some remaining quite small (Fig. 22, B and C); we may regard the latter as abortive spores, their suppression having allowed of the better nutrition of their surviving sister-cells. The mature spores show a triradiate marking on one side, probably lmL_. Fig. 21.—Calamostachys Binneyana. Part of tangential section of cone, showing portions of two whorls of bracts (br) with sporangiophores (sp) between. Around each of the latter the four sporangia' (sm) are grouped, br, free tips of other bracts, x about 25. S. Coll. 175. (G. T. G.) indicating the lines of junction with the sister-cells (Fig. 22, D). Numerous specimens of C. Binneyana, which is a fairly common fossil, have been examined, and no traces of more than one kind of spore have been found. Except for occasional abortion all the spores are uniform. There is thus a strong presumption that this species was homo- sporous. In another British species, however, Calamo- stachys Casheana, heterospory, as Williamson discovered, certainly occurred. In general organisation this cone is. 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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