Nature and development of plants . s, the involucre. The gametospore develops afterthe manner noted in Marchantia, forming a capsule with elaters,but its stalk or seta reaches much larger dimensions, owingdoubtless to the well-developed foot which penetrates the thallusand absorbs foods, thus making possible a larger sporophyte(Fig. 197, E). When the spores have been matured the setarapidly elongates to several times its original length, rupturingthe archegonium and lifting the capsule high in the air (; 197, A). The capsule usually breaks open into four valveswhich are hygroscopic, cl
Nature and development of plants . s, the involucre. The gametospore develops afterthe manner noted in Marchantia, forming a capsule with elaters,but its stalk or seta reaches much larger dimensions, owingdoubtless to the well-developed foot which penetrates the thallusand absorbs foods, thus making possible a larger sporophyte(Fig. 197, E). When the spores have been matured the setarapidly elongates to several times its original length, rupturingthe archegonium and lifting the capsule high in the air (; 197, A). The capsule usually breaks open into four valveswhich are hygroscopic, closing over the spores in damp weatherand opening in dry weather to expose them to the wind. Thesespores germinate and begin the life history of a new gam-etophyte. As in some of the Marchantiales a filamentous algal-like growth is first formed by the germinating spore before thecharacteristic plant is reproduced. 106. Order c. Anthocerotales or Horned Liverworts.—Thissmall group of three genera is the most interesting of all the. Fig. 198. One of the Anthocerotales, Anthoceyos, bearing four pod-shaped sporophytes, .?. The one on the right, s, has opened at the top andis discharging the spores, but elongation and the formation of spores con-tinues below owing to its basal growth. hepatics because it presents features that arc suggestive of thealgae and also of a relationship with the mosses and ferns. DEVELOPMENT OF PLANTS 265 The thallus is of a primitive type, often with simple lobingsand therefore, suggestive of relationship with the simplerJungermaniales (Fig. 198). A peculiar feature of the order isthe occurrence of mucilage cavities which communicate with theair through small openings on the under side of the cavities are always occupied by one of the blue-green , which possibly assists the plants in the retention of waterowing to their mucilaginous character. Another interesting fea-ture of the order is the occurrence of a single chloroplast in
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