E. palustre var. americana Vict., Contrib. lab. bot. Univ. Montreal 9:51. 1927.
E. palustre var. szechuanense Page, Fern Gaz. 11: 34. 1974.
Description:
Stems homophyadic, 20-80 cm tall (m 42), with internodes 2.5-5.8 cm
(m 3.8) and 1-3(5) mm in diameter (m 2.2), having 5-10 (m 7.4) ridges,
the angles prominent. Internally there is only carinal collenchyma and
the chlorenchyma is continuous around the stem. Central canal small,
about 1/6-1/3 diameter of stem, and vallecular canals nearly as large.
Endodermis outer common.
Sheaths elongated, 4-9 mm long (m 6.5), 2-5 mm wide (m 3.5), green
with long (2-5 mm, m 3.1 [North America m 3.7, Eurasia m 2.8])
narrow, black teeth, with scarious white margins. Sheath segments
and teeth with slight central grooves.
Branches spreading, in regular whorls from the middle nodes only, or
sparse, or absent. First internode shorter than the subtending stem
sheath, 2-5 mm long (m 3.2) with 4-6 ridges (m 5), the silica profile of
irregular tubercules. Branch teeth resemble stem teeth, with less
obvious scarious margins, commissure with long furrow (to 1 mm) of
anchorcells. Valleys rounded, with stomata scattered throughout.
Siliica pilules scattered over surface of stomate, but not outlining the
stomate. Stoma lined with a prominent double row of rod-like pilules.
Mamillae prominent, transversely aligned, confluent. Branches
hollow.
Cones 9-35 mm long (m 18.3) on peduncles 5-32 mm long (m 17.7).
Rhizomes shiny, black to dark brown, glabrous except on sheaths,
occasionally bearing tubers.
Spores 30-45 µm in diameter (m 39).
Gametophytes with plates obtusely lobed, sparse or absent in males.
Antheridia exserted, 3-5 times longer than wide, with 4-10 (mostly 8)
cap cells.
Type:
The sheet in the Linnaean herbarium (LINN), labeled "E.
palustris" (Packet 1241, sheet 5) actually contains two specimens of E.
arvense. Also noteworthy is that the specimen in Hortus Cliffortianus
listed by Linnaeus under E. arvense is actually E. palustre. Apparently
Linnaeus had trouble distinguishing these two species vegetatively,
even though his description in Species Plantarum makes clear that E.
arvense is heterophyadic, implying that E. palustre is homophyadic.
His phrase "caule angulato, frondibus simplicibus" points to E.
palustre as does the habitat "in Europe aquosis" and the specific
epithet, "marsh-loving". Hence, Hauke (1978) believes that his description clearly
indicates only one species, the plant presently known by his name,
and therefore it should be the type for the name E. palustre.
Seasonality:
Coning from June to August, may be earlier in southern
Eurasia.
Distribution:
North America south to New York, Michigan,
Illinois, Minnesota, North Dakota, Montana, Idaho, and California.
Eurasia south to the Mediterranean, Greece, Turkey, Kashmir, Tibet,
China, and Japan.
Ecology:
Sun and semi-shade, in swamps, marshes and other wet
places.
Discussion:
This species varies in size from region to region, being
generally more robust in more southerly areas. North American
specimens have been separated as a distinct variety by Victorin (1927)
on the basis of the sheath teeth being longer, more pointed, with
narrower scarious margins. More recently Page (1974) recognized a
variety in southwestern China, var. szechuanense, on the basis of long,
narrow sheath teeth with narrow scarious margins. It greatly resembles var. americana (Fig. 14-16).
Page illustrated micromorphological differences between typical E. palustre and his var. szechuanense
in support of his taxonomy, noting particularly the scattered rather
than transverse alignment of mamillae (and less confluence of them,
which would be a consequence of the lack of alignment). In this
character he finds E. palustre var. szechuanense to be
indistinguishable from E. telmateia. Hauke looked at one specimen he cited of
E. palustre var. szechuanense and found a pattern typical of E. palustre.
This micromorphological character of transverse alignment of
mamillae is more variable than Page realized (see discussion under E.
telmateia . Another character Page attributed to his var.
szechuanense, cones not exserted, may be a matter of age and development.
On one specimen he cited, Chu 3412, the cones appear to Hauke (1978) to be young,
and therefore not yet exserted. Although there is minor regional
variation in the sheath teeth, Hauke (1978) cannot find any justification for
recognition of any varieties of E. palustre.
Hauke (1978) had not seen specimens of E. palustre from California, but Mason
(1957) records it from San Mateo Co. Hauke did see in UC (UC 205082) a
specimen of the hybrid between E. palustre and E. telmateia, from
San Mateo Co., and that substantiates the presence of E. palustre
there.
HAUKE, R.L. (1978)
A taxonomic monograph of the genus Equisetum subgenus Equisetum.
Nova Hedwigia 30, p385.
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