. Lichens. Lichens. i88 REPRODUCTION spore which gradually grew out into delicate hyphae. AH these spores contain fat globules and finely granular protoplasm with a very large number of minute nuclei; the presence of the latter has been demonstrated by Haberlandt^ and later by Zopf^ who reckoned about 200 to 300 in the spore of Mycoblastus sanguinarius. These nuclei had continued to multiply during the ripening of the spore while it was still contained in the ascus^. Owing to the presence of the large fat globules the plasma is confined to an external layer close to the spore wall; the nuclei
. Lichens. Lichens. i88 REPRODUCTION spore which gradually grew out into delicate hyphae. AH these spores contain fat globules and finely granular protoplasm with a very large number of minute nuclei; the presence of the latter has been demonstrated by Haberlandt^ and later by Zopf^ who reckoned about 200 to 300 in the spore of Mycoblastus sanguinarius. These nuclei had continued to multiply during the ripening of the spore while it was still contained in the ascus^. Owing to the presence of the large fat globules the plasma is confined to an external layer close to the spore wall; the nuclei are embedded in the plasma and are connected by strands of protoplasm. The epispore in some of these large spores is extremely developed: in some Pertusariae it measures 4-5 /x in thickness. / POLARIBILOCULAR SPORES. The most peculiar of all lichen spores are those ;xm&A polaribilocularâsignifying a two-celled spore of which the median septum has become so thickened that the cell-cavities with their contents are relegated to the two poles of the spore, an open canal frequently connecting the two cell-spaces (Fig, 107). Other terms have been suggested and used by various writers to describe this unusual character such as blasteniospore^ orculiform* and placodiomorph^ or more simply polarilocular. The polarilocular colourless spore is found in a connected series of lichensâcrustaceous, foliose and fruticose {Placodium, Xanthoria, Teloschistes). In another series with a darker thallus {Rinodina and Physcid) the spore is brown-coloured, and the Fig. 107. Polarilocular spores, median septum cuts across the plasma-connection. a, Xanthoria parietina Th. ^ , , , .... Fr.; b,J? In Other respects the brown spore is similar to the S^',' '^'^^/"'',P"!^,<"'^f^"^^ colourless one and possesses a thickened wall with JNyl.; a, PnysciaciliansUQ. 'â x6oo. reduced cell-cavities. The method of cell-division in these spores resembles that known a
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