Equisetum L.

1. Equisetum L. View in CoL 2

Stems usually with a hollow in the centre surrounded by 2 rings of alternating smaller cavities. Leaves small, usually brownish.

Cones borne at the ends of the main stems and sometimes of the branches also. (Inch Hippochaete Milde.)

The only genus.

1 No green stems present

2 Sheathswith20-30 teeth; cone4-8cm 10. telmateia

2 Sheaths with 6-12 teeth; cone 1-4 cm 9. arvense

1 Green stems or stems with green branches present

3 Branches whorled

4 Mainstemc. 10 mmin diameter,branchedto apex, whitish, almost smooth, with 20-40 fine ribs 10. telmateia

4 Main stem rarely more than 7 mm in diameter, green; ribs well marked, less than 20, or upper part of stem without branches

5 Sheaths of main stem with broad, subacute teeth which are fewer than the grooves 7. sylvaticum

5 Sheaths of main stem with subulate teeth which are equal in number to the grooves

6 Central hollow at least f the diameter of the stem; teeth without ribs 5. fluviatile

6 Central hollow less than j the diameter of the stem; teeth with ribs 7 Lowest internode of branches much shorter than sheath on main stem; branches hollow 8 Stem usually with 6-10 grooves; central hollow less than I diameter of stem; cone obtuse 6. palustre 8 Stem with 8-20 grooves; central hollow more than i diameter of stem; cone apiculate 2. ramosissimum 7 Lowest internode of branches longer than sheath on main stem; branches solid 9 Central hollow c. ì diameter of main stem; branches mostly 4-angled, ascending or suberect 9. arvense 9 Central hollow c. | diameter of main stem; branches mostly 3-angled, horizontal or recurved 8. pratense

3 Branches absent or not in whorls

10 Cone apiculate; stems usually persistent; stomata below level of other epidermal cells

11 Teeth of leaf-sheaths caducous 1. hyemale

11 Teeth of leaf-sheaths persistent

12 Stem freely branched; central hollow c. i diameter of main stem 2. ramosissimum

12 Stem simple or branched only from base; central hollow c. i diameter of main stem, or absent 13 Central hollow c. | diameter of main stem; sheaths with 6-8 teeth 3. variegatum 13 Main stem solid; sheaths with 3-4 teeth. 4. scirpoides

10 Cone obtuse; stems not persistent; stomata superficial

14 Central hollow at least | diameter of main stem; teeth without ribs 5. fluviatile

14 Central hollow less than j diameter of main stem; teeth with ribs

15 Outermost cavities about the same size as the central hollow; branches hollow, their lowest internodes much shorter than sheath on main stem 6. palustre

15 Outermost cavities smaller than the central hollow; branches solid, their lowest internodes longer than sheath on main stem 9. arvense