Sheaths urceolate, elongate, 3-6 mm long (m 4.2), 1.5-3 mm wide (m 2.6), with short (1-3 mm long, m 1.9) brownish, papery teeth, the stem ridge grooves continuing up the center of each sheath segment.
Branches ascending, often dominating and obscuring the stem, sometimes few or absent on coniferous stems, the first internode 2-5 mm long (m 3.0), shorter than to nearly equaling the subtending stem sheath. Ridges 4, prominently grooved and bearing a silica profile of irregularly blocky tubercules, these at times obscure. Branch sheaths urceolate, with grooved segments bearing brown papery teeth, separated by commissures up to 0.6 mm long, furrowed, with distinct anchorcells. Valleys rounded, with stomata scattered throughout. Silica pilules scattered densely over the surface of the stomate, and distinctly outlining it but not lining the stoma. Mamillae transversely aligned, distinct to confluent. Branches solid.
Cones 15-24 mm long (m 17) on peduncles 10-16 mm long (m 14).
Rhizome dull dark brown, glabrous except on sheaths.
Spores 38-49 µm in diameter (m 43), occasionally aborted (Hauke 385, 391 from Colombia; UC m 077874 from Ecuador).
Gametophytes with plates narrow, often filamentous. Males lacking basal cushion, with anteridia on the plates. Antheridia much exserted, 10 times longer than wide, with 8-9 cap cells, these elongated to form a corona at dehiscence. Archegonial neck cells conspicuously elongated. Female gametophytes remain unisexual.
Kunkel (1964) described E. rinihuense from a single clone near a lake by Valdivia, Chile. It differs from E. bogotense in color, form, and ecological situation. From his description and photos, it is obvious that he had a stand where the main axes were aborted and replaced by branches. Some of these were secondarily branches, and the second-order branches had only 3 ridges instead of 4 (this is found in both E. bogotense and E. diffusum). The locale, a low stony bank on the lake, flooded during the rainy and snow-melt seasons, does not sound particularly unusual for E. bogotense, and would explain why the main stems were aborted. The only real distinction between E. rinihuense and typical E. bogotense remains the color difference. This is a regional variation Hauke noted among some Chilean specimens, but hardly seems sufficient basis upon which to recognize a distinct species. It is vague enough that Hauke would not even use it for a varietal character. With E. rinihuense, as with E. mekongense Page (see under E. diffusum) we see examples of "one plant" taxonomy, a highly questionable practice. True, Kunkel had a whole stand rather than a single specimen, but it most likely represented a single clone, hence a single genetic individual.
Milde (1867a) cited this species from Jamaica and British Guiana, but these locales appear doubtful. Hauke (1978) could discover no other record from either place.
HAUKE, R.L. (1978)
A taxonomic monograph of the genus Equisetum subgenus Equisetum.
Nova Hedwigia 30, p385.
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