. The essentials of botany. Botany. 264 PHYLUM X. CALAMOPHYTA in height, but in certain tropical species attaining a length of 10 meters or more. Among the better known are the Common Horsetail (Equisetum arvense), which sends up short lived, pale or brownish cone-bearing stems in spring, and profusely branching green stems in sum- mer (E. telmateia, the Great Horsetail of Europe and our own Northwestern region, resembles, but is larger than, the Common Horsetail); the Woodland Horsetail {E. sylvaticum), whose green cone-bearing stems branch profusely after fruiting, and persist all summer; an
. The essentials of botany. Botany. 264 PHYLUM X. CALAMOPHYTA in height, but in certain tropical species attaining a length of 10 meters or more. Among the better known are the Common Horsetail (Equisetum arvense), which sends up short lived, pale or brownish cone-bearing stems in spring, and profusely branching green stems in sum- mer (E. telmateia, the Great Horsetail of Europe and our own Northwestern region, resembles, but is larger than, the Common Horsetail); the Woodland Horsetail {E. sylvaticum), whose green cone-bearing stems branch profusely after fruiting, and persist all summer; and the Scouring-rush, called also Dutch Rush {E. hiemale), with green, branchless stems which produce cones, and survive the winter. The genus Equisetum originated in the Paleozoic period, and so is very old. Some of its species have become extinct, as is the case with several related genera. 473. The Old Calamites (Class Calamarinbae) were Paleozoic plants whose sporophytes were often trees, with hollow, jointed stems, whose collateral vascular bundles allowed an increase in diameter by the develop- ment of a cambial zone. The leaves were separate, narrow, and whorled at ophyte^and~sp??e3 the joiuts of the stem. The heterospores of 1 aiamite. -^ygj-g borne in terminal cones composed of whorls of sporophylls, each bearing one or more spo- rangia. Only fragmentary fossils of these plants are known. Laboratory Studies, (a) Collect in early spring a number of cone-bearing stems of the Common Horsetail. Note the joints (nodes), bearing whorls of united flat leaves, and the cone, composed of whorls of shield-shaped leaves (sporophylls). SpUt the cone and stem and note that the latter is hollow, with closed nodes. (6) Carefully dissect out a single sporophyll from the cone,. 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
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