. Botany of the living plant. Botany. :M BOTANY OF THE LIVING PLANT archegonium (Fig. 307). As it develops further the lower part remains thin, forming the seta, which maybe traversed by a conducting strand (Fig 305). But the distal part enlarges to form the capsule. A layer of cells is there cut off from the periphery of the endothecium, and acquires dense contents. This is the archesporium, which is shaped like a barrel without ends (arch. Fig. 305). Within it i= the large-celled water-storage tissue of the columella. The amphithecium, limited now bya superficial epi- dermis with stomata, fo
. Botany of the living plant. Botany. :M BOTANY OF THE LIVING PLANT archegonium (Fig. 307). As it develops further the lower part remains thin, forming the seta, which maybe traversed by a conducting strand (Fig 305). But the distal part enlarges to form the capsule. A layer of cells is there cut off from the periphery of the endothecium, and acquires dense contents. This is the archesporium, which is shaped like a barrel without ends (arch. Fig. 305). Within it i= the large-celled water-storage tissue of the columella. The amphithecium, limited now bya superficial epi- dermis with stomata, forms a lacunar photo-syn- thetic tissue, with a large and continuous air-space outside the archesporium. This tissue is specially active in that region called the apophysis, where the stomata are most frequent. In some Mosses it is enlarged as a very effective organ of nutrition. As the development proceeds the cells of the archesporium divide repeatedly, forming a thick cylinder of sporogenous cells surrounding the columella, and limited externally by a double layer of cells of the amphithecium. This con- stitutes the spore-sac. The cells then separate, and rounding off in a fluid that fills the sac, each undergoes tetrad-division, and finally produces four spores. Reduction takes place as usual, common numbers of chromosomes for Mosses being 12-6. The numbers are low for Bryophytes generally. The mature spore is very minute, and almost spherical, and it contains globules of oil. Meanwhile above the fertile region certain inner cells of the amphithecium undergo changes of induration of the cell-walls to form the peristome, which is closely related to the Uberation of the spores (Fig. 305). As its structure differs in detail in various Mosses, it provides facts valuable in their classification. The case of Fontinahs serves as a good example of a complicated peristome, as it is seen after the operculum falls away. It is double (Fig. 308). The inner peristome forms a sort of conne
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
