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Rh ridges. The accompanying cuts represent half-sections through the stems of the principal British species. In this species there are about a dozen blunt ridges on the stem, extending right to the points of the leaf-sheath. The branches are four-angled, solid, and jointed and sheathed like the main

Half-Sections through Horsetail Stems.

1. Equisetum maximum.

2. pratense.

3. arvense.

4. E. sylvaticum.

5. limosum.

6. palustre.

7. E. hyemale.

stem. The cells of the cuticle secrete silica in such quantity that the whole of the vegetable matter may be got rid of by maceration, yet the form of the stem will remain in this transparent skeleton of silica. Certain species are used for polishing metal, under the name of Dutch Rushes.

So far we have been describing what is known as the barren