Identifier: textbookofbotany00sach (find matches)
Title: Text-book of botany, morphological and physiological
Year: 1875 (1870s)
Authors: Sachs, Julius, 1832-1897 Bennett, Alfred W. (Alfred William), 1833-1902 Thiselton-Dyer, William T. (William Turner), 1843-1928
Subjects: Botany
Publisher: Oxford, Clarendon Press
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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same manner, but after their formation the sporangiumsplits at its apex, the spore slips out with a jerk and remains at rest, to germinate thenext night. In several other species (as V. sessilis, sericea, a.nd piloboloides) true zoosporesare formed. The preparations for them are similar to those in the last case; but thecontents of the branch which has swollen into a zoosporangium do not become sur-rounded by a cell-wall, but contract, showing in the interior one or more vacuoli, andthen escape as a naked cell from a fissure at the apex of the branch (Fig. 158, j4, sp).The escaped primordial cell contains numerous grains of chlorophyll surrounded bya layer of colourless protoplasm, and is everywhere covered by delicate densely crowdedshort cilia. Their vibratile motion causes a movement of the large ellipsoidal zoospore(as much as ^mm. long) about its longer axis, which sometimes, however, (as inV. sericea,^ lasts only for ^ to i§ minute. In F. sessilis the rotation begins, as I have
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Fig. i^B.—Vattcheria sessilis (X about 30). distinctly seen, during the escape from the sporangium; and if the opening is too small,the zoospore splits into two pieces; both become rounded off; the outer piece rotatesand swims out, while the inner piece rotates within the sporangium. As soon as thezoospores come to rest, the cilia disappear, and a cellulose-wall is produced (Fig. 158, B).The formation of the zoosporangia generally begins in the night; the spores escape inthe morning, and their germination commences the next night. The spore puts outeither only one or two tubes (C, X)), or it forms on the other side at the same time aroot-like organ of attachment (E, F, «u;). The Sexual Reproduction is brought about byoogonia (female cells) and antheridia (male cells). Both originate as twig-like protuber-ances from a branch or stem (Fig. 159, yl, B), sometimes even on the germinating tubeof the zoospore (Fig. 15S, F, og, b). All the species of Vaucheria are monoecious, and thetwo k

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