. Lichens. Lichens. 52 CONSTITUENTS OF THE LICHEN THALLUS a. Myxophyceae associated with Phycolichens. The blue-green algae are characterized by the colour of their pigments which persists in the gonidial condition giving various tints to the component lichens, and by the gelatinous sheath in which most of them are enclosed. This sheath, both in the lichen gonidia^ and in free-living forms, imbibes and retains moisture to a remarkable extent and the thallus containing blue-green algae profits by its power of storing moisture. Myxophyceae form the gonidia of the gelatinous lichens as well as of
. Lichens. Lichens. 52 CONSTITUENTS OF THE LICHEN THALLUS a. Myxophyceae associated with Phycolichens. The blue-green algae are characterized by the colour of their pigments which persists in the gonidial condition giving various tints to the component lichens, and by the gelatinous sheath in which most of them are enclosed. This sheath, both in the lichen gonidia^ and in free-living forms, imbibes and retains moisture to a remarkable extent and the thallus containing blue-green algae profits by its power of storing moisture. Myxophyceae form the gonidia of the gelatinous lichens as well as of some other non-gelatinous genera. Several families are represented^: Fam. Chroococcaceae. This family includes unicellular algae with thick gelatinous sheaths. They increase normally by division, and colonies arise by the cohesion of the cells. Several genera form gonidia: 1. ChroococcUS Naeg. Solitary or forming small colonies of 2-4-8 cells (Fig. 16) generally surrounded by firm gelatinous colourless sheaths in definite layers (lamellate). Chroococcus. is considered by some lichenologists to form the gonidium of Cora, a genus of Hymenolichens. 2. Microcystis Kiitz. Globose or subglobose cells forming large colonies surrounded by a common gelatinous layer (gonidia of Coris- ciuni). 3. Gloeocapsa Kiitz. (including Xanthocapsd). Globose cells with a. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smith, Annie Lorrain. Cambridge, At the University Press
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