This plant has a very thick rhizome from which arise the erect stems. The barren and the fertile stems closely resemble each other, being about a foot or more in height, with very rough surfaces on which it is possible to count from six to twelve very prominent ridges. The stems are enclosed at intervals in loose sheaths, which have the same number of teeth as the ridges on the stem. It should be noted that the branches from the various whorls show a marked tendency to turn upwards. On certain of the stems the fertile cone appears and the spores are ripened about June, after which the process withers. The plant as a whole remains green until late in the autumn. Sometimes in the case of large plants, cones have been known to occur on the tips of the branches of the Marsh Horsetail. The Marsh Horsetail is a very common species, often growing in the greatest profusion by the sides of pools. _Equisetum limosum._ In this case the specific name is a Latin word which means “full of mud”; this being an allusion to the fact that the plant favours swampy situations. The Smooth Naked Horsetail. The plant is also called the Water Horsetail. A distinctive feature of this plant is that it has almost completely smooth stems, though a close examination will indicate the presence of a number of slight ridges. The barren and the fertile stems are very similar, and in a favourable situation they will grow to the height of two or three feet. A curious feature of this plant is the irregular way in which the branches appear. Sometimes the stems are quite bare; on other occasions they are partly branched; in any case the branches are short. The sheaths with many teeth are closely pressed to the stem. The fertile stem is, of course, distinguished by the cone which it bears at the summit. It is said that cattle are not averse to eating the Smooth Naked Horsetail, and certainly the stems are not unpleasant to the touch. The Smooth Naked Horsetail is a common plant, specially by the sides of streams and pools. It sometimes grows right in the water. _Equisetum variegatum._ Here the specific name means variegated, and has reference to the fact that the sheaths enclosing the stem are pale green below and blackish in colour above. The Variegated Rough Horsetail.