. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 520 MOSSES AND FERNS CHAP. Pfeffer's figures, the cotyledons do not develop their vascular bundles until later. The early growth in length of the root is mainly intercalary, as the divisions in the apical cell for some time are not very rapid, and for a long time the root-cap con- sists only of the two original layers. With the growth of the embryo the cell-formation in the lower part of the spore continues until it is filled with a contin- uous large-celled tissue, the contents of whose cells
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 520 MOSSES AND FERNS CHAP. Pfeffer's figures, the cotyledons do not develop their vascular bundles until later. The early growth in length of the root is mainly intercalary, as the divisions in the apical cell for some time are not very rapid, and for a long time the root-cap con- sists only of the two original layers. With the growth of the embryo the cell-formation in the lower part of the spore continues until it is filled with a contin- uous large-celled tissue, the contents of whose cells are much less granular than the undivided regions of the spore, and as the embryo develops, the foot crowds more and more upon them until it nearly fills the spore cavity. On comparing Pfefifer's account of 5*. Martensii with my own observations upon 5". Kraussiana, the main differences consist first in the smaller devel- opment in the latter of the primary prothallium, i. e., the prothallial tissue formed before the spores are shed, the archegonia being only separated from the diaphragm by a single layer of cells instead of by three or four, as in S. Martensii. L. apus, which was also examined by the writer, is intermediate in this respect between the two. A second difiference is the later period at which the cell division in the lower part of the prothallium is S. Kraussiana. In this species, too, no rhizoids were seen, while Pfefifer observed them in 5". Martensii. Finally, in the latter the suspensor is much shorter and straighter than in 5". Kraussiana. Miss Lyon (2) found that in 5". apus no suspensor was formed, but the development of the embryo is not described. In S. Martensii, almost as soon as the cotyledons are estab- lished, the two-sided apical cell of the stem is replaced by a. Fig. 300.—Longitudinal section of a fully- developed prothallium of 5". Kraussiana, with an advanced embryo (em), X77; I, Please note that
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
