. A text-book of botany for secondary schools. Botany. HORSETAILS AND CLUB-MOSSES 199 pact group of modified leaves bearing sporangia. Just as in some ferns certain leaves are set apart to do chloro- phyll work and others to bear sporangia, so in the Equisetum the same division of work oc- curs; but the notable thing is that the spo- rangium-bearing leaves are massed together in a cluster that is quite distinct from the rest of the plant. Leaves set apart for bearing spo- rangia are called spo- rophylls, which means "spore leaves.' A strobilus, therefore, is a group of sporophylls that fo
. A text-book of botany for secondary schools. Botany. HORSETAILS AND CLUB-MOSSES 199 pact group of modified leaves bearing sporangia. Just as in some ferns certain leaves are set apart to do chloro- phyll work and others to bear sporangia, so in the Equisetum the same division of work oc- curs; but the notable thing is that the spo- rangium-bearing leaves are massed together in a cluster that is quite distinct from the rest of the plant. Leaves set apart for bearing spo- rangia are called spo- rophylls, which means "spore leaves.' A strobilus, therefore, is a group of sporophylls that form a more or less distinct cluster, dis- tinct from the rest of the plant. In Equisetum each sporophyll consists of a stalk-like portion and a shield-like top, be- neath which the several sporangia hang (Fig. 192, A). The spores have a very pecuHar outer wall. It consists of two spiral bands wound about the spore and fastened to it only at the point where they intersect (Fig. 192, B). When dry, the bands 14. Fig. 191.—Later sterile shoots of the species shown in Fig. 190, and photographed a month 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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