. Contributions from the Hull Botanical Laboratory. Plants. 170 BOTANICAL GAZETTE [SEPTEMBER spermatogenesis cell (figs. 20, 22). When only a single primary prothallial cell is cut off, it may (fig. 19) or may not (fig. 21) divide again. Far more frequently it does divide anticlinally. No case in either species has been observed where either prothallial cell divides periclinally. In case two prothallial cells are cut off, both usually divide anticlinally (figs. 23, 26, 27), although the division may be long delayed or fail wholly (text fig. 4). The first one may remain undivided, or in rare ca
. Contributions from the Hull Botanical Laboratory. Plants. 170 BOTANICAL GAZETTE [SEPTEMBER spermatogenesis cell (figs. 20, 22). When only a single primary prothallial cell is cut off, it may (fig. 19) or may not (fig. 21) divide again. Far more frequently it does divide anticlinally. No case in either species has been observed where either prothallial cell divides periclinally. In case two prothallial cells are cut off, both usually divide anticlinally (figs. 23, 26, 27), although the division may be long delayed or fail wholly (text fig. 4). The first one may remain undivided, or in rare cases may divide twice, so that the first tier of prothallial. Fig. i. Transverse section of a male gametophyte consisting of one prothallial cell (pi), the primary spermatogenous cell (ps), and the tube nucleus (t).—Fig. 2. Male gametophyte in which the primary spermatogenous cell has divided into the body cell (be) and the stalk cell (sc), and in which all the gametophytic walls have broken down.—Fig. 3. Same as the preceding except that there are four prothallial nuclei instead of one; it is uncertain whether they have been derived from one or two primary prothallial cells.—Fig. 4. A gametophyte with two primary prothallial cells (pIf p3) which have not divided, though the pollen is presumably ready for shedding.—Fig. 5. A gametophyte with a large stalk cell placed transversely to the axis of the body cell.—Fig. 6. Same as preceding except that there are four derivatives of the primary prothallial cell.—FlG. 7. A gametophyte in which the origin of the free nuclei is not easily traced; see text for discussion. cells contains four cells. The second one almost always divides once and usually twice. Thus there may be one, three, four, six, or eight prothallial cells; six is much the commonest number, and one or eight the rarest. In case only one prothallial cell is cut off, its nucleus. Please note that these images are extracted from scanned page images that may have
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