. Un manuel de botanique. La botanique. Le PILICINiE 137 PTERIDOPHYTA-Fig. 895. Le coussin est formé par les cellules de la ligne médiane dans la région antérieure divisant ensuite dans un plan parallèle à la surface de sorte que la masse devient plusieurs cellules d'épaisseur. Ce coussin porte l'archégone et peut d'une manière être comparé à l'archegoniophore de l'hépatiques. Les anthéridies ne se posent pas sur le coussin, mais vers la marge postérieure. Le anthcridium est toujours d'origine superficielle (fig. Toutes les cellules épidermiques naît et se divise en deux l'un de qui produit l'organe. Elle se divise en

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. A manual of botany. Botany. PTERIDOPHYTA—PILICINiE 137 the Fig. 895. The cushion is formed by the cells in the middle line in the anterior region then dividing in a plane parallel to the surface so that the mass becomes several cells in thickness there. This cushion bears the archegonia and may in a way be compared to the archegoniophore of the liverworts. The antheridia do not arise on the cushion, but towards the posterior margin. The anthcridium is always superficial in origin {fig. All epidermal cell grows out and is divided into two upper one of which produces the organ. It divides into two cells, the lower of which forms a stalk-cell. The upper one divides repeatedly, so as to form a wall surrounding a central cell, in which the mother cells of the antherozoids are pro- duced by repeated cell-divisions. In each mother cell a single antherozoid is pro- duced, which is a coiled filament furnished with cilia at its anterior end {fig. 860, b). When the antheridium is mature it ruptures, and the mother cells, containing the antherozoids, escape, the antherozoids being liberated a little later. The whole of the protoplasm of the mother cell is not used up to form the antherozoid, so that when the latter escapes it has usually attached to it a vesicle of protoplasm, the rest of the contents of the mother cell. The development of the arohegonium (fig. 897) is also from a superficial cell of the prothallium, which segments into two, an upper and a lower. The neck is de- rived from the former by a succession of divisions. It is much like the neck of the arohegonium of the moss, but much shorter, consisting of only a few tiers of cells. The lower cell grows upwards into the neck, separating its ceUs somewhat and forming the neck-eanal-ceU, which remains single. The neck-oanal-oeU is cut off from the remainder, which then constitutes the central cell of the arohegonium. This next outs off a small ventral-canal-cell, and the remainder rounds itself off into an ovoid ma

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• bookcentury1800
• bookdecade1890
• booksubjectbotany
• bookyear1895