Characters of the family. [Name ancient, signifying horse-tail, in allusion to the copious branching of several species.] Called also Toad-pip«, Tad-pipe.

About 25 species, of very wide geographic distribution. Type species: Equisetum ftuviatile L.

Stems annual; stomata scattered.

Stems of two kinds, the fertile appearing in early spring before the sterile.

Fertile stems simple, soon withering; sheaths of branches of sterile stems 4-toothed.


E. arvense.

Fertile stems branched when old, only the apex withering.

Branches of the stem simple, their sheaths 3-toothed.


E. pratense.

Branches compound.


E. sylvaticum.

Stems all alike; spores mature in summer; branches simple or none.

Sheaths rather loose; branches usually long; stems bushy below, attenuate upwards.

Central cavity very small; spike long.


E. palustre.

Central cavity about one-half the diameter of stem; spike short.


E. littorale.

Sheaths appressed; branches usually short.


E. fluviatile.

Stems mostly perennial, evergreen; spikes tipped with a rigid point; stomata in regular rows.

Stems tall, usually many-grooved.

Stems rough and tuberculate, prominently ridged.

Ridges with 1 line of tubercles; ridges of sheath tricarinate; stem stout.


E. robustutn.

Ridges of the stem with 2 indistinct lines of tubercles; ridges of sheath obscurely 4-

carinate; stem slender.


E. hyemale.

Stems not tuberculate; sheaths enlarged upward.


E. laevigatum.

Stems low, slender, tufted, usually 5-10-grooved.

Central cavity small; sheaths 5-10-toothed.


E. variegatum.

Central cavity none; sheaths 3-toothed.


E. scirpoides.