. Texte-livre de botanique, morphologiques et physiologiques. La botanique. 462 cryptogames vasculaires et intérieure. d'une cellule, de sorte qu'à ce stade, les jeunes prothalle est composé de quatre cellules courtes formant une ligne axiale mis fin au-dessus par la cellule apicale, ci-dessous par la cellule basale, et fermé latéralement par deux rangées de cellules. Il a été impossible de suivre le développement d'autres. Quinze ans plus tard (1872) Fankhauser trouvés en Suisse entièrement développé prothallia de Lycopodium annotinum parmi certaines mousses, dont l'un était toujours connecté à la jeune plante de la seconde génération (Fig. 326). L

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. Text-book of botany, morphological and physiological. Botany. 462 VASCULAR CRYPTOGAMS. inner and an outer cell, so that at this stage the young prothallium consisted of four short cells forming an axial row terminated above by the apical cell, below by the basal cell, and enclosed laterally by two rows of cells. It was impossible to trace the development any further. Fifteen years later (1872) Fankhauser found in Switzerland completely developed prothallia of Lycopodium annotinum among some Mosses, one of which was still connected with the young plant of the second generation (Fig. 326). These prothallia, which had grown in the absence of light, were irregularly lobed masses of cells of a pale yellow colour, furnished sparingly with small root-hairs. On the upper surface were numerous antheridia which are ovoid cavities in the tissue of the prothallium covered by a single layer of cells and filled with the very numerous mother-cells of the anthero- zoids. The form of the antherozoids themselves was not very clearly made out. These prothallia had no longer any archegonia, but they bore young plants: hence it ap- pears that Lycopodium produces only one kind of spores, a conclusion which is quite in accordance with the results of direct observation, and that the prothallia are monoecious, a peculiarity which at once sharply distinguishes the Lyco- podicese from the Isoetese and Selaginellese, as does also the very considerable size attained by the prothallium and its complete independence of the spore. Probably these conditions are the same in those genera which possess but one kind of spores, Psilofum, Tmesip/eris, Phylloglossum. The prothallia of Lycopodium evidently bear several arche- gonia, for Fankhauser found on them young plants in various stages of development. From the attachment of the young plant to the prothallium, it appears that the arche- gonia lie upon its upper surface in the grooves between the lobes. 2. The Asexual generation (Sporophore). From wh

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• bookcentury1800
• bookdecade1880
• booksubjectbotany
• bookyear1882