Bolander’s quillwort (Isoetes bolanderi) COSEWIC assessment and status report: chapter 5

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Species Information

• Name and Classification
• Morphological Description

Name and Classification

Scientific name:

Isoetes bolanderi Engelmann (1874)

Common name:

Bolander’s quillwort

Synonyms:

Isoetes californica Engelmann ex Gray (1867) - invalid name - listed in Gray (1867) without supporting information; Isoetes pygmaea Engelmann(1874); I. bolanderi var. pygmaea (Engelmann) Clute (1905) - depauperate form; Isoetes bolanderi Engelmann var. parryi Engelmann (1874) - shorter, thin-leaved plants with smaller-than-typical spores; Isoetes bolanderi Engelmann var. sonnei Henderson (1900) - depauperate form from Donner Lake, California.

Family:

Isoetaceae (Quillwort Family)

Major plant group:

Pteridophytes (fern-allies)

The scientific name and concept of this species is clear, with synonyms applying to populations now considered to be insignificant forms (Taylor et al. 1993). Isoetes bolanderi forms sterile hybrids with I. occidentalis Henderson and I. echinospora Dur. (I. xherb-wagneri Taylor) at its range periphery (Taylor et al. 1993). The most common is I. bolanderi x occidentalis, which occurs irregularly in the Sierra Nevada Mountains of California (DAO; Dfb; MICH; W.C. Taylor, pers. comm.). Isoetes x herb-wagneri is known from a single location in western Montana (Taylor 2002). No Canadian I. bolanderi hybrids are known.

Morphological Description

Isoetes bolanderi is a small quillwort with a cluster of soft-textured, straight, leaves 6-13 cm long, with extremes of 3 to 25 cm, projecting from a two-lobed corm (Figure 1). Corms are usually buried in the lake bottom and are not visible. Leaves typically are attached loosely and readily separate from the corm in response to even gentle physical impact (wave action, mechanical impact, etc.). They taper to a very fine point and vary from bright green to brownish-green. Sporangia, containing either megaspores or microspores, are embedded on the inner sides of the pale, inflated leaf bases. Each sporangium is partially covered (usually about 30%) by a translucent, plain-coloured velum (flap of tissue). The degree of coverage by the velum is an important taxonomic characteristic (Taylor et al. 1993, Brunton and Britton 1997, 1998).

Isoetes bolanderi is a true aquatic, occurring underwater and only rarely as an emergent along lakeshores (Engelmann 1882, Clute 1905, Pfeiffer 1922, Taylor et al. 1993). Canadian I. bolanderi plants are smaller than those in most of the species' range in the United States, typically ranging from 3 to 7 cm in height (D. Brunton, pers. obs.).

Isoetes bolanderi can easily be confused with the closely allied I. howellii Engelm., particularly in Canada (e.g. Taylor 1970). Isoetes howellii is an emergent or amphibious (rarely aquatic) species. It usually occurs at lower elevations in isolated, seasonally-inundated sloughs and along emergent lake and river shores in sites with geologically younger, more complex substrates (e.g. the metamorphic bedrock of the Columbia Highlands of the Shuswap Lake area of interior British Columbia). Isoetes howellii typically has longer, more narrow, recurved to reflexed leaves that vary from dark green to grayish green and which do not readily separate from the corm, as with I. bolanderi.

Figure 1: Single Plant of Isoetes bolanderi

x1 (Collection #10,841 by D. F. Brunton, Park County, Wyoming, August 1991).

Definitive identification of similar Isoetes species is normally difficult in the field since identification usually depends on examining the megaspore ornamentation, which requires dissection of the sporangia and high magnification.