. Lectures on the evolution of plants. Botany; Plants. ALG^ 69 including all the giant kelps, show only the simplest possible form of reproduction, purely non-sexual zoospores. Many of these larger kelps show an external differentiation which simulates closely the parts of the higher terrestrial plants. A definite axis, with lateral leaf-like outgrowths, has its base modified into a mass of firm root-like or- gans, forming a most efficient holdfast or an- chor, which, in some of the largest kelps, when torn away may carry with it a mass of rocks and shells weighing sev- eral hundred pound
. Lectures on the evolution of plants. Botany; Plants. ALG^ 69 including all the giant kelps, show only the simplest possible form of reproduction, purely non-sexual zoospores. Many of these larger kelps show an external differentiation which simulates closely the parts of the higher terrestrial plants. A definite axis, with lateral leaf-like outgrowths, has its base modified into a mass of firm root-like or- gans, forming a most efficient holdfast or an- chor, which, in some of the largest kelps, when torn away may carry with it a mass of rocks and shells weighing sev- eral hundred pounds. The leaves of the large kelps are often several metres in length, and although structurally they differ widely from those of the higher plants, yet functionally they must be considered as equivalent to these. It is in these organs that the greater part of the chlorophyll-bearing cells are situ- ated. The peculiar floats or air-bladders found in these plants are formed by the accumulation of gases within certain parts of the plant, resulting in a distention of the thallus at these points, but the details of their development cannot be given here. While some of the forms, including the larger kelps, appear to possess only non-sexual zoospores, others, like. Fig. 18 (Fucacese). — A, a fragment ol the common gull-weed, Sargassum, show- ing the definite stem and leaves, and the berry-like floats, v; B, the egg of the common rock-weed (Fucus vesi- culosus), being fertilized by the minute biciliate spermatozoids; C, a single spermatozoid more highly 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 Campbell, Douglas Houghton, 1859-1953. New York, The Macmillan Co. , London, Macmillan & Co. , Ltd.
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Keywords: ., bookcentury1800, bookdecade, booksubjectbotany, booksubjectplants
