1. Isotria medeoloides (Pursh) Raf. (small whorled pogonia)
Pl. 114 a, b; Map 467
Flowering
stems 9–25 cm tall, green. Flowers with stalks 4–6 mm long. Sepals 12–20 mm
long, only slightly longer than the petals, yellowish green to green, narrowly
oblanceolate to oblong‑linear. Lateral petals 12–17 mm long, yellowish
green, narrowly oblanceolate. Lip 10–15 mm long, obovate, the middle lobe
broadly rounded, white with green veins, with a longitudinal, yellowish green
crest that changes to bearded hairs toward the tip. Capsules with stalks 10–15
mm long. 2n=18. May–June.
Known
only from a single, historical collection from Bollinger County (eastern U.S. and adjacent Canada west to Missouri). Precise habitat unknown; specimen label reads “wooded
limestone hill.”
This
rare species was listed as Endangered by the U.S. Fish and Wildlife Service
under the federal Endangered Species Act, but the discovery of several new
populations in the northeastern United States caused its status to be revised
to Threatened in 1994. Plants are apparently self‑pollinated and have a
reduced rostellum that allows pollen to contact the stigma directly.
Efforts
to rediscover this species in Missouri have been hampered by the lack of a
precise habitat description on the label of Russell’s 1897 collection and the
inability to pinpoint the site of the single occurrence near Glen Allen in Bollinger County. Unlike I. verticillata, plants of the small whorled pogonia
usually are found singly, rather than in colonies. Elsewhere, the species
occurs primarily on acidic substrates, in a variety of hardwood and coniferous
forest types. At the single station in southern Illinois, plants grow on a
relatively dry, thinly wooded slope above a sandstone bluff. Further searches
for I. medeoloides may eventually result in its rediscovery in Missouri.