. A handbook of cryptogamic botany. Cryptogams. CCENOBIE^ 301 having in the meantime developed two ciha from each of its' Sexual reproduction takes place in the following way. Sixteen daughter- families are first of all formed in the same manner, but the gelatinous envelopes of the young colonies deliquesce, and the separate 256 (=16 X 16) swarm-cells are set free as zoogametes. These vary in size, but are always rounded and green at the posterior end, pointed hyaline and with a red pigment-spot in front, where they bear two cilia. Among the crowd of these swarm-cells—now swimming abou
. A handbook of cryptogamic botany. Cryptogams. CCENOBIE^ 301 having in the meantime developed two ciha from each of its' Sexual reproduction takes place in the following way. Sixteen daughter- families are first of all formed in the same manner, but the gelatinous envelopes of the young colonies deliquesce, and the separate 256 (=16 X 16) swarm-cells are set free as zoogametes. These vary in size, but are always rounded and green at the posterior end, pointed hyaline and with a red pigment-spot in front, where they bear two cilia. Among the crowd of these swarm-cells—now swimming about freely—some, irrespective of their relative size, approach one another in pairs, their pointed anterior apices coming into contact, and they finally coalesce into a body which has at first somewhat the shape of an hour-glass, but gradually contracts into a sphere, in which the two pigment-spots and the four cilia are still to be seen for a time, but soon disappear. This whole process occupies about five minutes. The resulting zygosperm is then a spherical cell enclosed in a cell-wall, which remains at rest for some time as a hypnosperm, its green colour becoming changed to brick-red. If the dried-up hypnosperms are placed in water, they begin to germinate after about twenty-four hours. The outer layer of the cell-wall is ruptured, an inner layer becomes gelatinous and swells up, and the protoplasmic contents escape in the form of one, two, or three large zoospores. Each of these, after a short period of swarming, loses its cilia, surrounds itself with a gelatinous envelope, and breaks up, by successive bipartitions, into sixteen portions, which develop cilia, and form them- selves into a new coenobe. A still more remarkable succession of phenomena is exhibited by Stephanosphara Cohn, a rare organism occur- ring occasionally in the rain- water which collects in the hollows of large stones in mountainous countries. In addition to the process of vegetative or non-sexual pro-
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