. The essentials of botany. Botany. 118 BOTANY. creeks and rivers we have an example of a filamentous plant of the class Zoosporese. It is a large, dark-green, much- branched plant, which attaches itself to stones and timbers in the water. It grows so vigorously that it soon forms long matted masses, often several metres in length, which float and wave back and forth in the currents of water. It pro- duces myriads of zoospores. 246. The Sea-Lettuce (Ulva), which is common along the coast and in brackish waters, grow- ing upon stones, wharf-timbers, etc., and resembling small lettuce-leaves, re
. The essentials of botany. Botany. 118 BOTANY. creeks and rivers we have an example of a filamentous plant of the class Zoosporese. It is a large, dark-green, much- branched plant, which attaches itself to stones and timbers in the water. It grows so vigorously that it soon forms long matted masses, often several metres in length, which float and wave back and forth in the currents of water. It pro- duces myriads of zoospores. 246. The Sea-Lettuce (Ulva), which is common along the coast and in brackish waters, grow- ing upon stones, wharf-timbers, etc., and resembling small lettuce-leaves, reproduces by zoospores. The plant is composed of a couple of layers of cells, and in some of these, by internal cell-formation, zoospores are produced; these escape into the water, where they swim about by means of their two cilia. 247. Kelp and its Allies (Phseo- sporese) make up a large group of zoospore-bearing plants. They are all marine, often attain a great size, and are of an olive-brown color. They con- stitute the Kelp which is often so abundant on the sea- shore after a storm. 248. The large, flat, leaf-like kelp (Laminaria, commonly called Devil's Apron) may be taken to illustrate the larger forms. The " leaf " portion is sometimes from one to six metres long and nearly a metre in breadth, while its stalk sometimes attains a length of two to four metres. It is held to rocks and stones at or below low-water mark by means of root-like processes. 249. The zoospores, which have two cilia, are produced. Fio. 51.—A plant o( Sea^let- tuce (Ulva lactuca). Natural. 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 Bessey, Charles E. (Charles Edwin), 1845-1915. New York : H. Holt and company, ;
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