Image d'archive à partir de la page 325 de la cyclopaedia de l'anatomie et. La cyclopaedia de l'anatomie et physiologie cyclopdiaofana05todd Année : 1859 slxteen embryon unicellulaire isolée de la même, avec son prolongement filamenteux, environ 150 diam, sa forme globulaire, jusqu'à ce qu'il se transforme en embryon, la direction de la croissance de l'axe de ce qui est vers le bas. 107, Orchis morio.- Dans l'Orchideae la structure de l'ovule est remarquablement simple. La description suivante de la mode d'origine et le développement précoce de l'embryon, de l'Orchis morio, dans toutes les étapes de ce que nous avons nous-mêmes suivies, est prise f

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Archive image from page 325 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana05todd Year: 1859 Isolated slxteen-celled embryo of the same, with its filamentous prolongation, about 150 diam, its globular form, until it is transformed into an embryo, the direction of growth of the axis of which is downwards. 107, Orchis Morio.— In the Orchideae the structure of the ovule is remarkably simple. The following description of the mode of origin and early development of the embryo, in Orchis Morio, all the stages of which we have ourselves followed, is taken from Mr. Hen- frcy's paper on Vegetable Reproduction, in the Annals of Natural History : — ' The ovule springs from the placental surface as a single projecting cell, which, by subdivision, soon becomes a cellular papilla (the nucleus), com- posed of a central cell (the embryo-sac), sur- rounded by a simple cellular layer. The two coats gradually grow up over this, and by the greater elongation of one side the ovule becomes anatropous. The nucleus mean- while loses its cellular coat, apparently by absorption, and appears as a large oval sac enclosed in the coats, consisting in fact merely 195. Early condition of ovule of Orchis mascula. The embryo-sac is exposed in consequence of the absorption of the cells which previously sur- rounded it, 180 diam. of an embryo sac. In the apex of this, about the epoch when the pollen falls upon the stigma, three cellules (embryonal vesicles), make their appearance at the upper end of Fig. 196. Isolated embryo-sac of the same immediately before impregnation, containing three embryonal vesicles, 180 diam. the embryo sac, formed apparently by free cell-formation around a globule of protoplasm. The pollen masses on the stigma send down pollen tubes, which traverse the conducting tissue of the style, and make their way to the placentas, where they enter, ordinarily, singly (sometimes more than one) into the micro- pyle canals of the ovule

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