. A text-book of botany for secondary schools. Botany. PERNS 195 spirally coiled bodies, blunt behind and tapering to a beak in front, the beak bearing numerous cilia (Fig. 188). The fern sperm, therefore, is a large, spirally coiled, multiciliate. Fig. 188.—Two antheridia of a fern (A), one containing sperms, the other discharg- ing them; also a single sperm much enlarged (/?). sperm, as compared with the small biciliate sperm of Bry- ophytes. With a ciliated sperm, fertilization can be effected only in the presence of moisture, and if prothallia are kept dry fertilization does not occur. In
. A text-book of botany for secondary schools. Botany. PERNS 195 spirally coiled bodies, blunt behind and tapering to a beak in front, the beak bearing numerous cilia (Fig. 188). The fern sperm, therefore, is a large, spirally coiled, multiciliate. Fig. 188.—Two antheridia of a fern (A), one containing sperms, the other discharg- ing them; also a single sperm much enlarged (/?). sperm, as compared with the small biciliate sperm of Bry- ophytes. With a ciliated sperm, fertilization can be effected only in the presence of moisture, and if prothallia are kept dry fertilization does not occur. In nature, however, the pro- thallia lying prostrate on the substratum are in a favor- able position for moisture; and when there is a film of mois- ture between the prothallium and the substratum the sperms caii swim to the archegonia. The oospore which is produced germinates at once and forms the leafy sporophyte (Fig. 186, B). The young stem and the root remain under the soil, but the young leaf is seen curving upward through the notch of the prothallium and growing up into the air and light. For a short time the young plantlet absorbs nourishment from the prothallium, but with its own root system and leaves it soon becomes. 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 Coulter, John Merle, 1851-1928. New York, D. Appleton
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1906
