. Lichens. Lichens. REPRODUCTIVE ORGANS 157 size, rarely more than i cm. in diameter (Fig. 88); there is no development in lichen fruits equal to the cup-like ascomata of the larger Pezizae. In. Fig. 88. Lecanora subfusca Ach. A, thallus and apothecia x 3; B, vertical section of apothecium. a, hymenium; by hypo- thecium; c, thalline margin or amphithecium; d, gonidia. X 60 (after Reinke). most cases the lichen apothecium retains its vitality as a spore-bearing organ for a considerable period, sometimes for several years, and it is strengthened and protected by one or more external margins of s
. Lichens. Lichens. REPRODUCTIVE ORGANS 157 size, rarely more than i cm. in diameter (Fig. 88); there is no development in lichen fruits equal to the cup-like ascomata of the larger Pezizae. In. Fig. 88. Lecanora subfusca Ach. A, thallus and apothecia x 3; B, vertical section of apothecium. a, hymenium; by hypo- thecium; c, thalline margin or amphithecium; d, gonidia. X 60 (after Reinke). most cases the lichen apothecium retains its vitality as a spore-bearing organ for a considerable period, sometimes for several years, and it is strengthened and protected by one or more external margins of sterile tissue. Immediately surrounding the fertile disc there is a compact wall of interwoven hyphae. In some of the shorter-lived soft fruits, as in Biatora, this hyphal margin may be thin, and may gradually be pushed aside as the disc develops and becomes convex, but generally it forms a prominent rim round the disc and may be tough or even horny, and often hard and car- bonaceous. This wall, which is present, to some extent, in nearly all lichens, is described as the "proper ; A second "thalline margin" containing gonidia is present in many genera': it is a structure peculiar to the lichen apothecium and forms the amphithecium. At the base of the apothecium there is a weft of light- or dark-coloured hyphae called the hypothecium, which is continued up and round the sides as the parathecium. merging into the " proper ; It forms the lining of a cup-shaped hollow which is filled by the paraphyses, which are upright closely packed thread-like hyphae, and by the spore-containing asci or thecae, these together constituting the thecium or hymenium. The paraphyses are very numerous as compared with the asci; they are simple or branched, ^ See also p. 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 perf
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