. Text-book of botany, morphological and physiological. Botany. FIG. 221.—A—D soredia of Usnea barbata; A a simple soredium, consisting of a gonidium covered with a web of hyphse; B a soredium, in which the gonidium has multiplied by division; C a group of simple soredia, resulting from the penetration of the hyphae between the gonidia; D, E germinating soredia; the hyphae are forming an apex of growth, and the gonidia are multiplying ; a-c soredia of Physcia parietina; a with an envelope of pseudo-parenchyma; b the envelope producing rhizines ; c a young thallus formed from a soredium (after
. Text-book of botany, morphological and physiological. Botany. FIG. 221.—A—D soredia of Usnea barbata; A a simple soredium, consisting of a gonidium covered with a web of hyphse; B a soredium, in which the gonidium has multiplied by division; C a group of simple soredia, resulting from the penetration of the hyphae between the gonidia; D, E germinating soredia; the hyphae are forming an apex of growth, and the gonidia are multiplying ; a-c soredia of Physcia parietina; a with an envelope of pseudo-parenchyma; b the envelope producing rhizines ; c a young thallus formed from a soredium (after Schwendener, X 500). closely to them and form an envelope of fibres. The gonidia divide repeatedly, and each daughter-cell is again woven over. This process is often repeated, the soredia accu- mulate in great numbers in the gonidial layer, and finally rupture the cortex. After. Fig. 222.—Examples of various Algae which act as the gonidia of Lichens (after Bomet); k in all cases is the hypha of the Fungus, and g the gonidium. A, germinating spore s of Physcia parietina, the hypha of which has attached itself to Pratococcus viridis; B, a filament oiScytonema invested by the hyphae of Stereocaulon ramtilosum; C, taken from the thallus of the Lichen, Physma chalaganum; a branch of the hypha is penetrating into a cell of the Nostoc-filament (gonidium); D, taken from the thallus of Synalissa symphorea, the gonidia are the Alga Glceocapsa; E, from the thallus oiCladonia Jurcata, the gonidium (Protococcus) is invested by hyphae. escaping in this manner, the soredia can still further multiply outside the thallus; but under favourable conditions either a single soredium or a mass of them grows out at once into a new thallus (Fig. 221). Schwendener states that in Usnea barbata this may occur. 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
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
