. The Canadian field-naturalist. Natural history. 98 The Canadian Field-Naturalist Vol. 111 Listera cordata (Linnaeus) R. Brown var. cordata Heart-leaved Twayblade Listere cordee Listera cordata, a tiny, inconspicuous plant found in a few swamps, is the only Listera species currently known in the District. It can be recognized by its pair of spreading, cauline leaves and its flowers that have spreading sepals and petals about half as long as the lip. The narrow lip has a deep notch between two long, narrow, point- ed, diverging lobes. Description Height: 7 (9 - 17) 22 cm [132 plants]. Flowers:
. The Canadian field-naturalist. Natural history. 98 The Canadian Field-Naturalist Vol. 111 Listera cordata (Linnaeus) R. Brown var. cordata Heart-leaved Twayblade Listere cordee Listera cordata, a tiny, inconspicuous plant found in a few swamps, is the only Listera species currently known in the District. It can be recognized by its pair of spreading, cauline leaves and its flowers that have spreading sepals and petals about half as long as the lip. The narrow lip has a deep notch between two long, narrow, point- ed, diverging lobes. Description Height: 7 (9 - 17) 22 cm [132 plants]. Flowers: 4 (6 - 12) 22 [123 plants]; sepals greyish green, lip and petals greyish green to brown; no odour detected. Leaves: 2; 2 on non-flowering plants. Overwintering State: a greyish green shoot, 1 - cm high, at the base of the current year's stem in the moss substrate; herbarium specimens show the new shoot present at anthesis. Capsules: greyish yellow, spheroid to ellipsoid, typically x cm, ascending (see Figure lb); yield averaging 60% [11 plants], similar to the 70% yield reported from California (Ackerman and Mesler 1979). Seeds: yellowish white, released in late June to early July while the flower parts are still fresh; this is by far the earliest release of seeds of any Ottawa District orchid. Blooming Period: 4 June (10 June - 28 June) 13 July [14 records]. Colony Sizes: 1 - 300 flowering plants [10 colonies], as scattered individuals and in loose groups. Distribution: The Ottawa District is well within the North American range of this transcontinental orchid. It is a species of the Montane, Boreal and Mixed Forest Regions. Within the District, L. corda- ta is thinly scattered across the Shield and in the Lowlands of the southwest. Habitat: Listera cordata is confined to semi- mature and mature coniferous swamps, usually in areas of calcareous bedrock. Plants occur in the. 76'' 30 Listera cordata var. cordata: â = herbarium specimen, sight record. The Canadian S
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