. The Characeae of America. nata (see Fig. 37), or they may, as in Ch. fragilis, closely converge. In the Nitellae the coronula is ten-celled ; the lower five cells are closely adherent, the five upper cells are less adherent, but of larger size. In some Nitellae the whole coronula is evanescent and drops off before the maturity of the spore. While the capsule is de- veloping and enclosing the spore, the latter has been growing and developing, in its interior, divis- ions which are not understood (Braun). In the Nitellae the di- vision takes place very early, be- fore the enveloping cells have
. The Characeae of America. nata (see Fig. 37), or they may, as in Ch. fragilis, closely converge. In the Nitellae the coronula is ten-celled ; the lower five cells are closely adherent, the five upper cells are less adherent, but of larger size. In some Nitellae the whole coronula is evanescent and drops off before the maturity of the spore. While the capsule is de- veloping and enclosing the spore, the latter has been growing and developing, in its interior, divis- ions which are not understood (Braun). In the Nitellae the di- vision takes place very early, be- fore the enveloping cells have scarcely attained the length of the terminal cell. At the top a flat disk is set off by a septum extending obliquely backward; then a second, also flat segment, follows, situated beneath the pos- terior wall of the first and reaching down to the base ; lastly, a third resting on the second, is set off from the basal surface. During this process the terminal cell grows on the anterior side so that a distortion of the tip is produced, the cell formation progressing Fl^. 41. downward and backward, and the anterior wall protruding toward the tip ; on this account the cells just described have been called the "turning ; In Chara a corresponding division occurs later, when the enveloping cells of the sporostegium have united over the central cell and is confined to a separation of a flat basal cell, like an internal spore pedicle, which is distinctly seen even till the spore be- comes ripe, while the "turning cells'' of the Nitellae, which do not increase in size, become difficult to recognize on account of the pre- mature development of the spore. After the separation of these structures, which seem to be devoid of significance in the farther de- velopment, the remaining part of the terminal cell changes to the ovule, which, when fertilized, ripens into the spore. The sporophydium reaches its full size, nearly, before fertilization. The ovule fills completely t
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