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Houstonia

Houstonia canadensis Willd. ex Roemer & J.A. Schultes was reported from ME by Gleason (1963), but specimens are unknown. Reference: Terrell (1996).

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H. caerulea
1a. Lower leaves borne on an evident petiole; corolla lobes horizontally spreading, glabrous; flowers borne singly on an elongate peduncle 20–70 mm long; capsule compressed; seeds globular, with a deep, round cavity on the inner face
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1b. Lower leaves sessile or with an obscure petiole; corolla lobes ascending to recurved, pubescent within the basal, connate tube; flowers borne multiple together in a cyme on pedicels 2–5 mm long [Fig. 882]; fruit not compressed; seeds meniscoid, with a ridge across the depression on the inner face
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  H. purpurea
  2a. Stem leaf blades broad-lanceolate to narrow-oblong, (4–) 5–12 mm wide, rounded at the base; sepals 3–6 mm long at anthesis
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  H. longifolia
  2b. Stem leaf blades broad-linear to narrow-oblong, 2–5 mm wide, narrowed to the base; sepals 1.5–2.5 (–2.7) mm long at anthesis

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