. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. PROTONEMA 287 The peristome-teeth are extremely sensitive to changes in the moisture-content of the air, curhng outwards when tire latter is dry, and inwards when it is damp. In dry weather, therefore, the powdery mass of spores inside the capsule is readilj' dispersed, whilst in wet weather the dome is reconstituted (Fig. 156, E), and the aperture, left by the shedding of the lid, closed. The actual dispersal, in which the elasticitj' of the seta plays a considerable part, is effected by a catapult-meclianis
. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. PROTONEMA 287 The peristome-teeth are extremely sensitive to changes in the moisture-content of the air, curhng outwards when tire latter is dry, and inwards when it is damp. In dry weather, therefore, the powdery mass of spores inside the capsule is readilj' dispersed, whilst in wet weather the dome is reconstituted (Fig. 156, E), and the aperture, left by the shedding of the lid, closed. The actual dispersal, in which the elasticitj' of the seta plays a considerable part, is effected by a catapult-meclianism similar to that of the Cowslip and Poppy Fig. 157.—Moss-protonema. A, Development of young Fimaria- plant (6.) from the protonema (p.) (after Campbell). B, Stages in germination of spores, and C, protonema of Dicranella heieromella (after Servettaz). ^., gemma on protonema ; r., rhizoids ; sp., spore-membrane. D, Single cell of overground part of protonema. The spores ultimately give rise to a new Liverwort or Moss, but the adult plant is not produced directly on germination. This is especially obvious in Mosses, where the spores in most cases develop into a branched multicellular filamentous structure, the protonema, which exists partly above and partly below ground (Fig. 157, C). The overground portion appears as a green weft on the surface of the soil, and its cells contain numerous discoid chloroplasts (Fig. 157, D), whilst the underground portion closely resembles the rhizoids of the ordinarj? Moss (Fig. 157, C, r.).. 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 Fritsch, Felix Eugene, 1879-; Salisbury, E. J. (Edward James), Sir, b. 1886. London, G. Bell and sons ltd.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpl, booksubjectplants
