The structure & development of the mosses and ferns (Archegoniatae) . n the youngprothallium. The spores quickly lose their power of germination, andshould be sown as soon as they are discharged. If this is donegermination begins almost at once, and within ten to twelvehours the first division wall may be completed. The chloro-plasts rapidly multiply by division and often show a distinct •^ Buchtien (i), p. 15. 424 MOSSES AND FERNS CHAP. radiae arrangement, extending in lines from the nucleus to theperiphery. The first division may occur before the spore haschanged form, and in this case (Fig.
The structure & development of the mosses and ferns (Archegoniatae) . n the youngprothallium. The spores quickly lose their power of germination, andshould be sown as soon as they are discharged. If this is donegermination begins almost at once, and within ten to twelvehours the first division wall may be completed. The chloro-plasts rapidly multiply by division and often show a distinct •^ Buchtien (i), p. 15. 424 MOSSES AND FERNS CHAP. radiae arrangement, extending in lines from the nucleus to theperiphery. The first division may occur before the spore haschanged form, and in this case (Fig. 218, C) a small cell is cutoff by a strongly curved wall. Both cells contain chlorophyll,but the nucleus of the smaller cell is smaller than the other spores there is first an elongation, as in Osmunda, andthe smaller end, which like that has some chlorophyll, but notso much relatively as the larger, is cut off, and forms the firstrhizoid, and within twenty-four hours, under suitable conditions,this may reach a length considerably exceeding the diameter. Fig. 219.—Young prothallia of Egtcisetum, showing the variation in form, X i8o. In A there is apparently a definite initial cell; r, rhizoid. of the spore. Sadebeck ^ showed and Buchtien confirmedthis, that the first root-hair is positively heliotropic. The first divisions in the prothallial cell are extremelyvarious, in this recalling the behaviour of the eusporangiateFilicineae and the Osmundaceae. The first wall may be eithervertical or transverse (Fig. 2 18), and sometimes, but not often,there are several transverse walls, short filament is commonly the first transverse wall is followed by avertical wall in one or both cells. In case the first wall isvertical it not infrequently happens that the two cells, byrepeated transverse divisions, form two parallel rows of cells,which may diverge, so that the young prothallium becomes two- ^ Sadebeck (6), p. 177. - Buchtien (i), p. 29. XIII EQUISETINE
Size: 1763px × 1417px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
