. The natural history of plants, their forms, growth, reproduction, and distribution;. Botany. THALLOPHYTA. 663 this stalk are attached a series of long ribbon-like leaves, each of which, just at its point of insertion upon the stem, swells into an air-bladder about the size of a pigeon's egg. Thus the stem, which is attached below, is buoyed up, and the long leaves depend into the water. In structure the stem is not unlike that of a Lami- naria; but it possesses in addition to the medulla, with its trumpet hyphse, a zone containing large sieve-tubes, which resemble those con- tained in the so
. The natural history of plants, their forms, growth, reproduction, and distribution;. Botany. THALLOPHYTA. 663 this stalk are attached a series of long ribbon-like leaves, each of which, just at its point of insertion upon the stem, swells into an air-bladder about the size of a pigeon's egg. Thus the stem, which is attached below, is buoyed up, and the long leaves depend into the water. In structure the stem is not unlike that of a Lami- naria; but it possesses in addition to the medulla, with its trumpet hyphse, a zone containing large sieve-tubes, which resemble those con- tained in the soft bast of a Flower- ing Plant (c/. vol. i. fig. 10*, p. 45, and fig. 125 ^ p. 469). Nereocystis, occur- ring on the W. coast of , consists of a long stalk (attaining to a length of nearly 100 metres), at- tached at its lower extremity and ex- panding above into a huge retort- shaped air-sac, from the surface of which a number of fronds (6-10 metres in length) arise. Like Macrocystis, its stem contains well- marked sieve-tubes. It is used by the Aleutians as fish- ing-line. Of La- minariacese about 90 species have been distinguished (including 30 species of Laminaria). FucacecB.âIncludes a number of the larger common sea-weeds. They are characterizedâlike the last familyâby a segmentation into a well-marked shoot and organ of attachment. The former is usually flattened and branched, and often bears air-bladders. Reproduction is by means of spermatozoids and non-ciliated egg-cells, which arise in flask-shaped hollows (conceptacles) on definite portions of the shoot or frond. Asexual reproduction by detachment of â a&iC: Fig. 37e.âFucus vesiculosus. 1 Vertical section through a female conceptacle. 2 a single oogonium from the conceptacle surrounded by sterile hairs, s A detached oogonium containing 8 egg-cells; the inner lamella of the wall is much swollen. * Liberation of the egg-cells. ix50; 2,3,4x160. (After Thuret.). Please note that these images
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1895
