. Studies in fossil botany . Paleobotany. 453 STUDIES IN FOSSIL BOTANY entering the seed. The multicellular structure of the pollen-grains, in this and other cases, was first demon- strated by Renault, and fully confirmed by the more recent observations of Oliver, who finds that there are about twenty cells in each grain, so arranged that five radial septa are seen when the grain is cut transversely. Fig. 173-—Stcphanospcrmuiit a-kenioides. Upper part of pollen-chamber, showing part of its wall, with the base of the beak. In the chamber a large multicellular pollen- grain is shown, also three
. Studies in fossil botany . Paleobotany. 453 STUDIES IN FOSSIL BOTANY entering the seed. The multicellular structure of the pollen-grains, in this and other cases, was first demon- strated by Renault, and fully confirmed by the more recent observations of Oliver, who finds that there are about twenty cells in each grain, so arranged that five radial septa are seen when the grain is cut transversely. Fig. 173-—Stcphanospcrmuiit a-kenioides. Upper part of pollen-chamber, showing part of its wall, with the base of the beak. In the chamber a large multicellular pollen- grain is shown, also three small foreign pollen-grains, one of which partly overlies the large grain. X 90. Will. Coll. 1486a. From a photograph leat by Prof. F. W. Oliver, (Fig. 174). Ultimately the internal cells appear to have become retracted towards the periphery, leaving behind them in the middle of the grain a framework of cell- wall—the " replum " (see Fig. 174). In the light of our present knowledge of the repro- duction of Ginkgo and the Cycads it is an obvious suggestion that the internal cells of the pollen- grain were antheridial cells, producing 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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