. Lectures on the evolution of plants. Botany; Plants. 114 EVOLUTION OF PLANTS phases, the protonema and gametophore. The spore on germination produces a filamentous, or occasionally flat, alga-like growth, the protonema (Fig. 29, A, B, C, pr'), and upon this arise special buds or branches which grow into leafy stems, the gametophores (Fig. 29, A, B, C, A), which bear the sexual The leaves of the gameto- phoric branches are commonly arranged spirally, and the branches seldom are flattened as in the foliose Hepaticae. While there are cer- tain superficial resem- blances between the lea
. Lectures on the evolution of plants. Botany; Plants. 114 EVOLUTION OF PLANTS phases, the protonema and gametophore. The spore on germination produces a filamentous, or occasionally flat, alga-like growth, the protonema (Fig. 29, A, B, C, pr'), and upon this arise special buds or branches which grow into leafy stems, the gametophores (Fig. 29, A, B, C, A), which bear the sexual The leaves of the gameto- phoric branches are commonly arranged spirally, and the branches seldom are flattened as in the foliose Hepaticae. While there are cer- tain superficial resem- blances between the leafy stems of the mosses and foliose liverworts, there are differences which make it extremely improb- able that the former have been derived from the latter. The two forms are rather to be considered as parallel developments. In the Musci the structure of both leaves and stem is as a rule much more complex than in the HepaticEB, and there is usually present a central strand of conducting tissue, quite wanting in both stem and leaf in the latter Fig. 29 (Mnsci or True Mosses).—A, the liverwort-like protonema of a peat- moss (Sphagnum) with theleafy shoot, k, budding out from It; B, the fila- mentous protonema, pr, of a common moss (Funaria), with a very young leafy bud, k\ C, an older stage of the same moss; D, the full-grown leafy gametophore, g, with the sporophyte, sp, still connected with it; ar, the re- mains of the archegonium carried up by the growth of the 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, London, The Macmillan company
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