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Crocanthemum
See list of 4 species in this genusOur frostweeds have traditionally been treated as part of the genus Helianthemum; however, recent phylogenetic evidence, as well as morphology and distribution, supports separating New World ( Crocanthemum) from Old World ( Helianthemum) species (Arrington and Kubitzki 2003). Species of Crocanthemum produce two types of flowers—chasmogamous flowers with showy yellow petals and cleistogamous flowers that lack petals. The chasmogamous flowers also have larger sepals and larger capsules that contain more seeds than the cleistogamous ones. Reference: Daoud and Wilbur (1965).
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1a. Chasmogamous (i.e., petaliferous) flowers solitary (rarely paired) at the summit of the stem during anthesis, later overtopped by lateral branches [Fig. 584]; capsules of cleistogamous flowers with 5–14 seeds; seeds papillose; pedicels and calyx sometimes with red, glandular hairs (in addition to stellate and simple hairs); adaxial surface of leaf blades, especially the young ones, with both short, stellate hairs and longer simple hairs 0.5–1 mm long
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2a. Mature stems with widely divergent branches; cleistogamous capsules 3–4.5 mm wide, with 8–14 seeds; seeds with low, broad papillae; adaxial surface of mid-stem leaf blades typically with dense stellate pubescence, the hairs so abundant as to have overlapping branches that obscure view of the epidermis
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2b. Mature stems with ascending branches [Fig. 584]; cleistogamous capsules 2–3 mm wide, with 5–10 seeds; seeds with long, slender papillae; adaxial surface of mid-stem leaf blades typically with moderate stellate pubescence, the hairs usually spaced so that the branches are separate and not overlapping and the epidermis is visible
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1b. Chasmogamous flowers in corymbs of 2–20 flowers at the summit of the stem during anthesis, only sometimes overtopped later in season by lateral branches [Fig. 583]; capsules of cleistogamous flowers with 1 or 2 (–3) seeds; seeds indistinctly reticulate; pedicels and calyx lacking glandular hairs, with only stellate and simple, eglandular hairs; adaxial surface of the leaf blades with only stellate hairs, lacking simple hairs
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3a. Stems scattered along a creeping rhizome; outer sepals (i.e., the narrower ones) of cleistogamous flowers apically distinct for a distance of 0.2–0.5 mm, the distinct tip 1–2 times as long as wide; capsules of cleistogamous flowers somewhat rounded in cross-section; leaf blades narrow-cuneate at base
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3b. Stems ± clustered at the tips of caudex branches; outer sepals of cleistogamous flowers apically distinct for a distance of (0.3–) 0.6–1.2 (–1.8) mm, the distinct tip mostly 3–5 times as long as wide; capsules of cleistogamous flowers sharply 3-angled in cross-section; leaf blades cuneate at base [Fig. 583]
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Each photo represents one species in this genus.