The structure & development of the mosses and ferns (Archegoniatae) . Fig. 147.—Isoetes echinospora var. Brauiiii (Dur.). A, Longitudinal section through the apex ofthe female prothallium, showing the first cell formation, x 300 ; B, similar section of a prothalliumwith the divisions completed and the first archegonium (ar) already opened. parallel with the base of the cover cell, and divides it into theprimary canal cell and central cell. The contents of the three 2«2 MOSSES AND FERNS CHAP. cells of which the archegonium is now composed are similar,and the nuclei large and distinct. The cover
The structure & development of the mosses and ferns (Archegoniatae) . Fig. 147.—Isoetes echinospora var. Brauiiii (Dur.). A, Longitudinal section through the apex ofthe female prothallium, showing the first cell formation, x 300 ; B, similar section of a prothalliumwith the divisions completed and the first archegonium (ar) already opened. parallel with the base of the cover cell, and divides it into theprimary canal cell and central cell. The contents of the three 2«2 MOSSES AND FERNS CHAP. cells of which the archegonium is now composed are similar,and the nuclei large and distinct. The cover cell next dividesinto four by transverse walls (Fig. 146, E), and from these, as inMarattia, the four rows of cells of the neck are formed. Thenumber in each row is four in the mature archegonium. Theventral canal cell, which like that of Marattia extends thewhole breadth of the central cell, is separated almost simul-. FiG. lifi.— Isoetes echinospora var. Brait7iiiiji\yc.). Development of the archegonium, X 500 ; o, theegg; V, ventral canal cell; h, neck canal cell ; D shows a two-celled embryo within the arche-gonium. taneously with the appearance of the first transverse divisionsin the neck cells. The neck canal cell has at first a singlenucleus, which later divides, but there is no division wallformed. Although the number of cells in each row of theneck is usually greater than in Marattia, the neck canal cellis shorter and extends but little between the neck cells (, B). The ^^% is very large, round or oval in form, and the IX iWA/^A rriACE/E—ISOETA CE^ 283 nucleus contains a lar<;e round body (nucleolus ?) that stainsvery intensely, but otherwise shows little chromatin. Thereceptive spot is of unusual size, and occupies about one-thirdof the egg. It is almost hyaline, showing, however, a faintreticulate arrangement of fine granules ; the lower portion ofthe Qg^ is filled with granu
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
