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Ferns of the Sierra (1960) by Robert J. Rodin


ISOETACEAE
QUILLWORT FAMILY

ISOETES

Perennial plants either submerged, amphibious or terrestrial. Stem forms a condensed 2 or 3-lobed corm; numerous roots branch dichotomously. Leaves are broad at base, tapering to an awl-like apex, 3 or 4-angled in cross-section appearing hollow, but actually having 4 longitudinal rows of air chambers. Many leaves, ultimately becoming sporophylls which bear microspores or megaspores on their inner side at the base of the leaf. Sporangia, flattened on one side, are never larger than about Vs inch in diameter and may or may not be covered with a membrane called a velum. According to Frye, one microsporangium produces 150,000 to 300,000 microspores and one megasporangium produces 150 to 300 megaspores. One leaf will bear only one of these kinds of spores. The sculpturing of the sporangia walls by various spines, ridges and reticulations is important in the classification of the species. This is the only genus in the family and contains about 60 species with worldwide distribution according to Abrams.

KEY TO THE SPECIES:

Submerged aquatic, 2-lobed corm I. bolanderi
Terrestrial in damp places, 3-lobed corm I. nuttallii

BOLANDER’S QUILLWORT

Isoetes bolanderi Englm. (Figs. 54, 55)

Corm 2-lobed, 5 to 20 leaves, 2 to 6 inches long, tapering like a quill, hence the common name. Megaspores marked with minute spines and wrinkles, microspores spiny.

In shallow ponds and lakes from 5,000 to 10,000 feet elevation in the Sierra Nevada including such places as Siesta Lake, Dog Lake, and ponds in many meadows in Yosemite. It is also known from British Columbia to Wyoming, in Colorado, and Arizona.

NUTTALL’S QUILLWORT

Isoetes nuttallii A. Br. (Fig. 55)

Corm 3-lobed, 15 to 60 leaves per plant, leaves 3 or 4 inches long, slender. Megaspores variable in size, smooth or warty; microspores brown, covered with spinelike papillae.

A terrestrial species found on the banks of streams, or more common in the Sierras in shallow soil under the mist of waterfalls. Distributed throughout California, Oregon, Washington, Idaho, and Lower California.

Fig. 54 BOLANDER’S QUILLWORT (Isoetes bolanderi)
[click to enlarge]

Fig. 54 BOLANDER’S QUILLWORT (Isoetes bolanderi). Upper: Growing in a typical shallow lake of the Sierra where water is no deeper than four feet. Lower: Close-up of this species from the above lake.

Fig. 55 Left: NUTTALL’S QUILLWORT (Isoetes nuttallii). Right: BOLANDER’S QUILLWORT (Isoetes bolanderi)
[click to enlarge]

Fig. 55 Lower left: NUTTALL’S QUILLWORT (Isoetes nuttallii). Swollen leaf bases contain sporangia. This species grows in the mist of waterfalls with its roots in soil. Right: BOLANDER’S QUILLWORT (Isoetes bolanderi). Showing comparative size to the first species. Upper insert: One leaf or sporophyll of the latter species with its sporangium at the base.



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