. Lectures on the evolution of plants. Botany; Plants. PTEEIDOPHYTA 145 In Selaginella (Fig. 38), while the embryo closely resembles that of Lycopodium, the gametophyte is very different. The sporophyte produces two sorts of spores, large and small. The former, the macrospores, produce a rudimentary gametophyte, which bears only archegonia (Fig. 38, E). The gametophyte projects from the spore but little, and until its later stages is contained entirely within the macrospore. In germination there are first. Fig. 38 (Lycopodinese). — A, a branch of one of the smaller club-mosses (Selaginella) wi
. Lectures on the evolution of plants. Botany; Plants. PTEEIDOPHYTA 145 In Selaginella (Fig. 38), while the embryo closely resembles that of Lycopodium, the gametophyte is very different. The sporophyte produces two sorts of spores, large and small. The former, the macrospores, produce a rudimentary gametophyte, which bears only archegonia (Fig. 38, E). The gametophyte projects from the spore but little, and until its later stages is contained entirely within the macrospore. In germination there are first. Fig. 38 (Lycopodinese). — A, a branch of one of the smaller club-mosses (Selaginella) with two sporangial spikes, sp; B, longitudinal section of spike showing a single macrosporangium, ma, and several mlorosporau- gia, mi; C, germinated microspore containing the rudimentary male gametophyte; v, the single vegetative cell; an, the antheridlum; D, a spermatozoid (after Belajeff); E, germinating macrospore with the female gametophyte protruding; ar, archegonia; F, a single arche- gonium; G, a young embryo, em., attached to the suspensor, sus, whose base remains within the archegonium; H, young sporophyte, still at- tached . to the gametophyte within the macrospore; cot, cotyledons; r, root. produced within the spore numerous free nuclei, be- tween which, later, cell-walls arise, forming a continuous tissue much as in the "embryo-sac" of the flowering plants. The formation of the gametophyte begins in Selaginella before the spores are set free from the sporangium. The small spores or microspores produce an even more rudimentary gametophyte (C), which is. 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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