. A handbook of cryptogamic botany. Cryptogams. 26 VASCULAR CRYPTOGAMS chlorophyll, but never loses its connection with the megaspore, even after the commencement of the germination of the sporophyte. The first archegone makes its appearance on the elevated dorsal ridge of the prothallium, and subsequently two others are formed, one on each side of the first. If one of these is fertilised no more archegones are pro- duced, and the prothallium ceases growing. But if no impregnation has taken place the prothallium continues to grow, and produces from one to three additional rows, each consisting
. A handbook of cryptogamic botany. Cryptogams. 26 VASCULAR CRYPTOGAMS chlorophyll, but never loses its connection with the megaspore, even after the commencement of the germination of the sporophyte. The first archegone makes its appearance on the elevated dorsal ridge of the prothallium, and subsequently two others are formed, one on each side of the first. If one of these is fertilised no more archegones are pro- duced, and the prothallium ceases growing. But if no impregnation has taken place the prothallium continues to grow, and produces from one to three additional rows, each consisting of from three to seven archegones. In Azolla the prothallium has the form of a slightly convex disc, consisting, in its central part, of several layers of cells, at the margin of only one. A single WJ^ archegone is first formed, near the centre of the prothallium. If this. Fig. 9.—Salvinia naians. Longitudinal section through megaspore and prothallium. a, wall of sporange; ^, epispore, formed of hardened mucilage; c, coat of" spore ; d, diaphragm separating prothallium from spore-cavity ; ^r, prothallium; m, neck of archegone ; /, //, first two leaves of embryo ; j, scutiform leaf or cotyledon. (After Pringsheim, x 70.). 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 Bennett, Alfred W. (Alfred William), 1833-1902; Murray, George Robert Milne, 1858-. London, New York, Longmans, Green, and Co.
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