. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . in mucilage. In the discoidal forms the Coleochaetaceae 315 branches are all procumbent and in some species concrescent (C. scutata,C. orbicularis), in which case the thallus is a more or less parenchymatousdisc one layer of cells in thickness (fig. 207). In C. soluta the procumbentfilaments are not concrescent and the disc consists of branched filamentsradiating from a central point. In other species the ramification is notconfined to one pl
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . in mucilage. In the discoidal forms the Coleochaetaceae 315 branches are all procumbent and in some species concrescent (C. scutata,C. orbicularis), in which case the thallus is a more or less parenchymatousdisc one layer of cells in thickness (fig. 207). In C. soluta the procumbentfilaments are not concrescent and the disc consists of branched filamentsradiating from a central point. In other species the ramification is notconfined to one plane (C. irregularis, C. pulvinata), but numerous ascendingbranches are given off, the whole thallus sometimes forming a hemisphericalcushion. Growth is peripheral and due to the divisions of the terminal cellsof the branches, which in the discoidal forms are the marginal cells of thedisc. In some species the branching is apparently dichotomous, but in othersit much resembles that of Cladophora or Stigeoclonium. Some of the cells of the thallus are always furnished with sheathedbristles. Each bristle is a long colourless hair issuing from a narrow. Fig. 207. Coleocheete scutata Breb. x 100. cylindrical basal sheath (up to 50 p, in length). Pringsheim (60) originallydescribed these bristles as jointed or septate; and Lambert (10) has recentlyasserted that, notwithstanding the fact that this articulation has not beenrecognized by Jost (95), Wille (97), Chodat (98), West (04), Oltmanns (04),or Collins (09), the bristles of some young Coleocfu&te-pl&nts he examinedwere distinctly articulate. It is not improbable, however, that this articu-lation is only apparent, as in Aphanochsete, and that the bristles are nottruly septate. Lambert found that the bristles attained a length of45 mm. The most curious species of the genus is C. Nitellarwm Jost (95;Lewis, 07), which is endophytic in the outer layers of the wall of speciesof Nitella. In consequence of its habit the cells are grea
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