Text-book of structural and physiological botany . ed ^Ice-land moss, Cetraria islandica)^ swell up, when boiled inwater, into a homogeneous jelly, forming the so-called* moss- or lichen-starch, or Lichenin. Among the organs of reproduction of Lichens are thesoredia (Fig. 409 iv.), which are developed in the gonidial 288 Siriicht7al and Physiological Botany, layer ; groups of gonidia becoming enclosed in peculiarfibrous envelopes, and, when so completely inwoven, grow-ing rapidly, and thus exercising a pressure on the cortexwhich ruptures it. The soredia which protrude through thecrevices caus
Text-book of structural and physiological botany . ed ^Ice-land moss, Cetraria islandica)^ swell up, when boiled inwater, into a homogeneous jelly, forming the so-called* moss- or lichen-starch, or Lichenin. Among the organs of reproduction of Lichens are thesoredia (Fig. 409 iv.), which are developed in the gonidial 288 Siriicht7al and Physiological Botany, layer ; groups of gonidia becoming enclosed in peculiarfibrous envelopes, and, when so completely inwoven, grow-ing rapidly, and thus exercising a pressure on the cortexwhich ruptures it. The soredia which protrude through thecrevices caused in this way increase in the same manner ordevelope into new individuals. In addition. Lichens arealso provided witli spermogonia and spermatia^ correspond-ing in all respects to those of the Ascomycetes. Finally,they also possess peculiar receptacles or apothecia (Fig. 409I., p. 285). These are either open from the first, and thenexpand and bear the hymenial layer on their surface (); or they open only at the apex by a narrow canal ; or. Fig. 413.—Vertical section through the middle of a young apotheciuin of LecajtoraS7ibfusca ; the club-shaped asci are developed at the apex oi the ascophorou^-hyphae, and lie imbedded in the hymenium ; the layers at each side containspherical gonidia ( x loo). they remain closed, and enclose a fertile nucleus. Hyme-nial layers of the first kind correspond to the receptacles ofthe Discomycetes, and the Lichens to which they belongare called gymnocarpoiis ; those of the two last kinds re-semble the perithecia of the Pyrenomycetes, and theLichens are called a7igioca7pous. The development of theapothecia always begins in the interior of the mature they consist of the external tissue orexcipiihim ; of a layer in which larger and stouter hyphalfilaments are developed than those found in the remainderof the tissue, the ascophorous hyphce or subhymenial layer;and of the true hymenial layer^ composed of parallel hyphaeox paraphy
Size: 2353px × 1062px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, bookpublishernewyorkjwileysons
