. College botany; structure, physiology and economics of plants. Botany. 300 COLLEGE BOTANY gether. The spores are borne within this structure. The mar- ginal cells for abo'Ut two-thirds of the circumferemces are small and thick-walled, while the others are large and thin-walled. When mature the absOirption of water by and evaporation fro^m this ring of cells is uneven, resulting in a rupturing of the spo- rangium and a scattering of the spores. These spores germinate and produce new prothallia or The Differemiiaiion of the Sporophylls, Sporangia and Spores.—It will be readily s
. College botany; structure, physiology and economics of plants. Botany. 300 COLLEGE BOTANY gether. The spores are borne within this structure. The mar- ginal cells for abo'Ut two-thirds of the circumferemces are small and thick-walled, while the others are large and thin-walled. When mature the absOirption of water by and evaporation fro^m this ring of cells is uneven, resulting in a rupturing of the spo- rangium and a scattering of the spores. These spores germinate and produce new prothallia or The Differemiiaiion of the Sporophylls, Sporangia and Spores.—It will be readily seen that the leaves (or fronds) of the ferns serve two very distinct functions, photosynthesis and Fig. 147. Fig. 145. Fig. Fig. 145.—Young fern leaf showing method of unrolling. Fig. 146.—Part of fern leaf showing sori or fruit clusters. Fig. 147.—Part of fern leaf showing sori with indusium. Fig. 148.—Sporangium from fern sorus. Fig. 149.—Fern spores from sporangium. bearing sporangia which contain non-sexual spores. The photo- synthetic function is the same in all chlorophyll-bearing plants. The leaves of some ferns perform both functions. A fern leaf which bears sporangia is known as a sporophyll. The leaves of some ferns are so differentiated that certain parts serve for bearing sporangia only. In other species certain leaves^ serve one function and others serve the other function. Furthermore, in some species of the Pteridophytes certain sporophylls bear microsporangia and others macrosporangia; the former being known as microsporophyUs and the latter as macrosporophylls. The microsporangia bear microspores which produce male. 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 Cook, Melville Thurston, 1869-1952. Philadelphia and London, J. B. Lippincott Company
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1920
