. Dansk botanisk arkiv. Plants; Plants -- Denmark. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 231 The specimen from an exposed place which I am going to describe was growing upon Amphiroa fragilissima originating from a coral reef at the south coast of St. Croix, The specimens found here are scarcely 1 cm, high. Their colour is more or less bluish green, while specimens from more protected places and from deep water have a red brown colour. The thallus consists of a central ramified filament composed of large cylindrical cells near the upper end of which a whirl of 4 di- or trichotomous
. Dansk botanisk arkiv. Plants; Plants -- Denmark. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 231 The specimen from an exposed place which I am going to describe was growing upon Amphiroa fragilissima originating from a coral reef at the south coast of St. Croix, The specimens found here are scarcely 1 cm, high. Their colour is more or less bluish green, while specimens from more protected places and from deep water have a red brown colour. The thallus consists of a central ramified filament composed of large cylindrical cells near the upper end of which a whirl of 4 di- or trichotomously ramified branchlets are issued (Fig. 219). The basal part of the fila- ments is decumbent and fastened to the host plant by means of rhizoids. In the most vigorously developed rhizoids the stalk is moniliform owing to the oval shape of the thickwalled cells, in the less vigorous cylindrical; the stalk ends in short, irregularly ramified filaments often forming a small disc. These rhizoids grow out from the basal cell of the branchlets (Fig. 220). The cells in the central fila- ments are cyhndrical with thick walls; in vigorous filaments they reach a length of about 180 // and a breadth of 120/^. They are not corticated. The branchlets are repeatedly di- or trichotomously ramified ; the cells in the branch- lets are broadest and shortest near the base, tapering gradually upwards growing at the same time longer. The uppermost ones, in any case in the lower part of the thallus, are often long cylin- drical growing up between the filaments of the branchlets above, and because of this, covering in most cases the main stem quite densely (Fig. 219). In the cells of the branchlets we find well developed chro- matophores. These consist of a parietal campanulate plate, down- wards with large openings or with irregularly shaped prolongations. In the cells of the central filaments the chromatophores, on the. Fig. 219. Crouania attenuata Bonnern.) J. Ag. Part of a main filament with br
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