Equisetum sylvaticum L., Sp. Pl. 1061. 1752.

E. capillare Hoffm., Fl. Deutsch. 3.1795.
E. sylvaticum var. multiramosum (Fernald) Wherry, Amer. Fern J. 27: 58. 1937.

Description:

Stems heterophyadic, the vegetative 25-70 cm tall (m 43), with inter- nodes 2.3-6.5 cm long (m 4.1) and 1.5-3 mm in diameter (m 2.5), having 8-18 ridges (m 11.6), these flattopped, with two rows of silica tubercules, which at times become long and spiculate in the upper part of the internode. Internally both carinal and vallecular collenchyma present, and chlorenchyma present under the ridges only. Central canal 1/2-2/3 diameter of the stem, endodermis outer com- mon in stem, double common in rhizome.

Sheaths squarish, 3-6 mm long (Z 4.2), 2.5-6 mm wide 3 3.9) with teeth long (3-10 mm, X 5.2), reddish brown, papery, and usually laterally coherent into 3 or 4 groups.

Branches in regular whorls, delicate, arching, branched, the first internode longer than the subtending stem sheath, 5-9 mm long (m 6.9). Ridges 3 or 4 (rarely 5), the silica profile of small points, open exaggerated in the first internode, or absent. Teeth narrow, pointed, spreading. Commissure obscure. Valleys channeled, with stomata in a single line (occasionally doubled) on either side. Silica pilules outlining the stomate, lining the stoma, but sparse over the surface. Mamillae small, in longitudinal rows.

Coniferous stems at first non-chlorophyllous and unbranched, but after spore discharge becoming green and branched. Measurements other than height generally exceeding those of the vegetative stems, and stem ridge tubercules less developed.

Cones 15-30 mm long (m 22) on peduncles 20-65 mm long (m 39).

Rhizomes shiny, light brown, smooth, covered with hairs, occasionally bearing tubers.

Spores 30-49 µm in diamter (m 41).

Gametophytes with plates sparse or absent on the male. Antheridia protuberant, 2-4 times longer than wide, with 2-6 (mostly 4) cap cells.

Type:

LINN packet 1241 sheets 1 & 2. (Sheet 1 is a coniferous stem, sheet 2 has two vegetative stems). The two were pinned together by Linnaeus. Sheet 3, which also contains a vegetative stem of E. sylvaticum, was labelled "E. arvense" by Linnaeus, and pinned to sheet 4, which is E. arvense.

Seasonality:

Coning April and May, later in the far north.

Distribution:

North America south to Virginia, Ohio, Iowa, Nebraska, Montana, Idaho, Washington. Eurasia south to the Mediterranean (rarely), the Balkans, USSR north of Crimea, and the Caspian region, across Siberia to Manchuria, Korea and Hokkaido, Japan.

Ecology:

Moist open woods, swamps, prairies, meadows, wet banks.

Discussion:

This species is the most attractive member of the subgenus, because of its lacy appearance, the result of its fine, compound branches. The Eurasian plants tend to be larger than the American. They also tend to have the silica on the first branch internode better developed. Fernald (1918) treated the less scabrous North American populations as a separate variety (for nomenclatural purposes he created the ungainly combination E. sylvaticum var. pauciramosum Milde, forma multiramosum Fernald). Fasset (1944) studied the occurrence of scabrosity in mass collections from Maine to Alaska, and found that there was complete intergradation from scabrous to glabrous, and that there was a cline of increasing scabrosity across the continent from Maine to Alaska (see Table).

Scabrosity of E. sylvaticum across North America (modified from Fassett, 1944)
Locality NGlabrous IntermediateScabrous
Maine 8185% 15% 0%
Ontario 7179% 21% 0%
Wisconsin14966% 31%3%
Minnesota 4430% 45%25%
South Dakota 5618% 43%39%
Alaska 3119% 23%58%

Fassett reported that even among the stems from one rhizome there can be variation in amount of scabrosity. He wrote, "Some will argue that such an intergrading series merits no nomenclatural recognition, even in the subspecific categories, but it appears to me, as it did to Professor Fernald and to Dr. Wherry, that if the extremes in the series show some geographic segregation the varietal designation is indicated." Hauke is among those who would argue against it, particularly since this one character shows no correlation with other characters.

HAUKE, R.L. (1978)
A taxonomic monograph of the genus Equisetum subgenus Equisetum.
Nova Hedwigia 30, p385.
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