The New Student's Reference Work/Equisetales
Equisetales (ĕk′wĭ-sē̇-tā′lēz), one of the three great plant-groups which make up pteridophytes, commonly known as horsetails or scouring rushes. In early geological times the group was of great importance, and was represented by a great display of forest-forms. At present it contains but a single genus (Equisetum), represented by about twenty-five species. The equisetums have a very characteristic body. The stem is slender and jointed, and the joints separate easily. It is also green and fluted, and there is so much silica in the epidermis that the plants feel rough. It is on this account that the name scouring rush is sometimes used. Foliage leaves have been abandoned, but minute scale-leaves form sheaths at each joint. The stems are sometimes simple, at other times they branch profusely, but they are always green, since they do leaf-work. At certain times a cone-like structure, the strobilus, appears at the top of the stem, which bears the sporangia containing spores. Horsetails are found in wet ground or in very dry ground. Slender branching forms are very common along the sandy embankments of railroads. See Pteridophytes.