A Manual of Aquatic Plants

PART II: DESCRIPTIVE TREATMENT

PART II DESCRIPTIVE TREATMENT GREEN ALGAE RED ALGAE CHLOROPHYCEAE RHODOPHYCEAE These are shapeless masses of microscopic green threads. Sometimes they are attached to stones or to larger plants, and sometimes they float as bubble-filled scum. The Green Algae include a vast number of genera and species the identification of which is possible only with the aid of a microscope; a few of the common forms, however, can be recognized in the field with the use of a hand lens, but in all cases determinations should be verified by a microscopic examination. 1. Threads forming a net, visible to the unaided eye (Figs. 1, 2). Hydrodictyon, the Water Net. 1. Threads not forming a net ................................................ 2 2. Threads with a silky, slippery feel; a mass, when picked up, tapering at its lower end to a corkscrew tip (Fig. 3) .................................... 3 2. Threads of a cottony texture, not slippery................................ 4 3. Chloroplast spiraled (Figs. 4, 5, 6). Spirogjra. 3. Chloroplast star-like (Fig. 7). Zygnema. 4. Plants floating, not attached ............................................ Ii 4. Plants attached to stones or sticks...................................... 7 Ii. Threads freely branching (Figs. 9, 10, 12). Clad6phora and Rhizocl~nium. Ii. Threads branching slightly or not at all .................................... 6 6. Threads about as thick as a hair (Fig. 12). Rhizocl~nium. 6. Threads finer than cotton fibers (Figs. 14, 15). Oedog~nium and some of its relatives. 7. Plants forming a close felt-like mass. VaucUria. Fig. 8. 7. Plants not close and thread-like........................................... 8 8. Threads with a head-like cluster of branches (Figs. 11, 13, 16). Batrachospermum and Draparnlldia. 8. Threads without head-like clusters...................................... 9 9. Fine unbranched ~hreads in cold, constantly flowing water. tnothrix. Figs. 17,18. 9. Fine or coarse threads, somewhat branched (Figs. 9, 10, 12). Clad6phora and Rhizocl~nium. Reference: The most useful comprehensive work on Algae is The Fresh-water Algae of the United States, by G. M. Smith, published by McGraw-Hill Book Company , Inc. STONEWORTS, MUSKGRASS CHARAcEAE This family of Algae is unique in its possession of cylindrical whorled branches. ERflh joint of the stem consists of a single cell. The plants 36 ALGAE Hydrodictyon: 1. Portion of plant, X 5. 2. Portion of plant, X 1. Spirogyra: 3. Bit of plant held by forceps, X 1. 4, 5, 6. Different species, X 300. Zygnema: 7. Part of plant, X 300. Vaucheria: 8. Part of plant, X 100. Cladophora: 9. Part of plant, X 50 10. Part of plant, X 300. 37 ALGAE Batrachospermum: 11. Plant, X 5. 1:3. Part of plant, X 25. of plant, X 300. Oedogonium: 14, 15. Parts of plant, X 150. of plant, X 300. UJothrix: 17, 18. Parts of plants, X 300. 38 RhizocJonium: 12. Part DraparnaJdia: 16. Part ./ Cap 22 CHARA, NITELLA Chara: 21. Oogoniulll, X 45. C. vulgaris: 19. Plallt, X 1. C. aspera: 20. Plant, X I. Nitella: 22. OogoniullI, X 45. N. ftexilis: 23. Plant, X I. N. hyalina: !H. Plant, X I. 39 40 MOSSES AND LEAFY LIVERWORTS almost always occur in hard water and often have incrustations of lime. The two genera here described can sometimes be differentiated by use of a hand lens, but for certainty the tip of the oogonium (egg-bearing case) must be examined with a microscope. The illustrations (Figs. 19-24) show but a few of the many species. 1. Plants rough and harsh, appearing lined (Fig. 21) when seen with a lens; oogonium (Fig. 21) capped by 5 cells. Chua. Figs. 19-21. 1. Plants smooth (Fig. 22); oogonium capped by 10 cells (Fig. 22). Nitella. Figs. 22-24. BLUE-GREEN ALGAE CYANOPHYCEAE Gelatinous balls, of bluish-green color, from the size of a pinhead to that of a walnut or even larger, attached to rocks or to plants, sometimes free-floating and rolled by the waves in shallow water. Several genera occur, the commonest being Nostoc, but their identification is entirely dependent on the use of a microscope. Reference: Josephine Tilden, Minnesota Algae, University of Minnesota, 1910. The title is misleading; this treats the Blue-green Algae only, and includes all known in North America. MOSSES LEAFY LIVERWORTS MUSCI HEPATICAE Mosses and Liverworts (together comprising the Bryophytes) reproduce by microscopic spores borne in capsules (Figs. 33, 35). They are separated, technically, on the manner of opening of the capsule. For convenience, the Leafy Liverworts are here treated with the Mosses, which they superficially resemble, and the Thallose...