Text-book of botany, morphological and physiological . ents of the cell are perfectly homogeneous; the antherozoid originates from ashining scarcely granular mass of protoplasm which encloses a vacuole, the ciliaat one end being formed first, and the spiral body becoming differentiated frombefore backwards by a kind of splitting of the protoplasm. The antherozoid is 403 originally curved spirally round the central vacuole; this latter, surrounded by afine membrane, not unfrequenlly remains attached to the posterior end of theantherozoid after it has escaped, and is carried along
Text-book of botany, morphological and physiological . ents of the cell are perfectly homogeneous; the antherozoid originates from ashining scarcely granular mass of protoplasm which encloses a vacuole, the ciliaat one end being formed first, and the spiral body becoming differentiated frombefore backwards by a kind of splitting of the protoplasm. The antherozoid is 403 originally curved spirally round the central vacuole; this latter, surrounded by afine membrane, not unfrequenlly remains attached to the posterior end of theantherozoid after it has escaped, and is carried along by it. The movement doesnot last longer than five minutes in the antherozoids of Isoetes, in Selaginella fromone-half to three-quarters of an hour. From the commencement of germinationtill the complete maturity of the antherozoids there is, in Isoetes, an interval ofabout three weeks; the same period from the dissemination of the spores is neces-sary in Selaginella. The JMacrosporcs produce the female prothallium, which is an endogenous struc- fV^:^. Fig. 303.—Germination of Selaginella (after Pfeffer); /—///, S. Martensii, A—D, S. caulescens; I longitudinal section of amacrospore filled with the prothalliinn and endosperm,* d the diaphragm, ee two embryos in process of formation ; //a youngarchegoniuni not yet open ; /// an archegonium with the oospore fertilised and divided once ; A a microspore showing theprimordial cells; B C different views of these divisions; D the mother-cells of the antherozoids in the perfect anther-idium. ture in a still higher degree even than is the case with Rhizocarps. In this respectand in the mode of its development, it shows a still greater resemblance to the tissuethat fills up the embryo-sac of Gymnosperms, and even of Angiosperms. In Isoetesthe cavity begins to be filled with cellular tissue a few weeks after the escape of themacrospores from the decaying macrosporangium; the cells of this tissue are all atfirst still naked (without c
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
