. Principles of modern biology. Biology. The Plant Kingdom - 599 PLATES. Fig. 31-4. Flame algae (Pyrrophyta). The dinoflagel- lates (shown above) are the most important of the flame algae. Note the unique arrangement of the flagella and the overlapping cellulose plates. Some dinoflagellates produce toxic substances and are re- sponsible for "mussel poisoning" and "red tides" (see text). the millions when an upsurging population of dinoflagellates becomes so great that it is described as a "red ; Also "mussel poi- soning" may result when people eat m
. Principles of modern biology. Biology. The Plant Kingdom - 599 PLATES. Fig. 31-4. Flame algae (Pyrrophyta). The dinoflagel- lates (shown above) are the most important of the flame algae. Note the unique arrangement of the flagella and the overlapping cellulose plates. Some dinoflagellates produce toxic substances and are re- sponsible for "mussel poisoning" and "red tides" (see text). the millions when an upsurging population of dinoflagellates becomes so great that it is described as a "red ; Also "mussel poi- soning" may result when people eat mussels that have been feeding mainly upon toxic dinoflagellates. The Dinoflagellata and other Pyrrophyta appear to have initiated a separate path of evolution at a very early date, as is indicated in Figure 29-11. The Phaeophytes (Brown Algae). About 1000 species of these marine algae are found, mainly in shallow coastal waters, although some species extend their range to depths approaching 100 feet. The species vary widely from small branching filamentous forms, such as Ectocarpus (Fig. 31-5), to large expansive plants, such as Laminaria (Fig. 31-5). All possess fucoxanthin and chlorophyll in vary- ing proportions; and the color ranges from light greenish brown to very dark, almost blackish green. The larger brown algae, which sometimes are called kelps, may show a considerable differentiation of their organs. Character- istically, there is a holdfast (Figs. 13-3 and 31-5), a branching stemlike stipe, and a num- ber of broad leaflike blades. Also there may be a number of gas bladders (Fig. 31-5), which buoy up the thallus, so that the blades receive a maximum share of the weak light that filters down through the overlying water. Some brown algae, compared to other algal forms, display a high degree of cellular differentiation. At the center of the stipe in some brown algae, are found a number of elongate cells with perforated end walls, somewhat like the sieve tubes of higher
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