. Plant studies; an elementary botany. Botany. THE GEEAT GROUPS OF ALGiE 249 teristic coast forms. All of them are anchored by holdfasts, which are sometimes highly developed root-like structures; and the yellow, l)rowu, or olive-green floating bodies are buoyed in the water usually by the aid of floats or air-bladders, which are often very conspicuous. The kelps are most highlj developed in the colder waters, and form much of the " wrack," " tangle," etc., of the coasts The group is well adapted to live exposed to waves and cur- rents with its strong holdfasts, air-ljladde
. Plant studies; an elementary botany. Botany. THE GEEAT GROUPS OF ALGiE 249 teristic coast forms. All of them are anchored by holdfasts, which are sometimes highly developed root-like structures; and the yellow, l)rowu, or olive-green floating bodies are buoyed in the water usually by the aid of floats or air-bladders, which are often very conspicuous. The kelps are most highlj developed in the colder waters, and form much of the " wrack," " tangle," etc., of the coasts The group is well adapted to live exposed to waves and cur- rents with its strong holdfasts, air-ljladders, and tough leathery bodies. It is what is known as a specialized gr0112}—that is, one which has become highly organ- ized for certain special condi- tions. It is not our purpose to consider such a specialized group in any detail, as it does not usual- ly help to explain the structures of higher groups. 170. The plant body.—There is very great diversity in the structure of the jjlant body. Some of them, as Ectucar- ^j(/,s (Fig. 217), are fil- amentous forms, like the Confervas among the Green AlgK, but others are very much more complex. The thallus of Lam- inar ia is like a huge floating leaf, frequently nine to ten. Fui. "217. A brown alga <,Ectocarpus). showing a body consisting of a simple filament which puts out branches (.4), some sporangia (_B) contain- ing zoospores, and gametangia {C) containing gametes.— 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 Coulter, John Merle, 1851-1928. New York, D. Appleton and Company
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