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FNA | Family List | FNA Vol. 8 | Saxifragaceae

19. Boykinia Nuttall, J. Acad. Nat. Sci. Philadelphia. 7: 113. 1834.

[For Samuel Boykin, 1786-1848, planter, physician, and naturalist of Milledgeville, Georgia]

Richard J. Gornall

Neoboykinia H. Hara; Therofon Rafinesque

Herbs, rhizomatous, not stoloniferous (± stoloniferous in B. intermedia). Flowering stems erect, leafy, 10-130 cm, densely stipitate-glandular and eglandular-pubescent. Leaves in basal rosette and cauline; cauline leaves similar to basal, gradually reduced distally to sessile bracts; stipules present; petiole densely stipitate-glandular; basal leaf blades reniform to reniform-orbiculate or cordate, shallowly lobed to deeply cleft, base cordate, ultimate margins crenate to serrate, apex acute or rounded, surfaces stipitate-glandular, adaxial surface grooved over veins; venation palmate. Inflorescences compound, dichasial cymes, terminal from terminal bud in rosette, branches (3-)5-20(-30)-flowered, bracteate. Flowers ± radially symmetric; hypanthium adnate 1/2-5/6 to ovary, free from ovary 0.7-3 mm, usually green, sometimes purple; sepals 5, green to purple; petals 5, white (sometimes with pink veins in B. richardsonii); nectary tissue encircling base of styles at junction of ovary and free hypanthium; stamens 5; filaments linear to subulate; (anthers apiculate or obtuse); ovary 2/3 to completely inferior, 2-locular, carpels connate proximally; placentation axile; styles 2; stigmas 2. Capsules 2-beaked. Seeds (ca. 50-500), usually black, (brown in B. richardsonii), ellipsoid, tuberculate (smooth in B. richardsonii). x = 7.

Species 7 (6 in the flora): North America, nw Mexico, e Asia (Japan).

The Japanese species is Boykinia lycoctonifolia (Maximovicz) Engler, which, based on its morphology, seems to be most closely related to B. aconitifolia.

1 Inflorescence branches 3-flowered; seeds smooth.   6 Boykinia richardsonii
+ Inflorescence branches 5-30-flowered; seeds tuberculate   (2)
2 (1) Leaf blades usually orbiculate-cordate, sometimes reniform, lobed to 1/2 their lengths; stipules of cauline leaves expansions from petiole base   (3)
+ Leaf blades usually reniform, rarely cordate, lobed to 1/2-3/4 their lengths; stipules of cauline leaves foliaceous or expansions from petiole base   (4)
3 (2) Petals 2-3 times as long as sepals; basal leaf blades usually 3-9-lobed.   4 Boykinia occidentalis
+ Petals shorter than or to 1.5 times as long as sepals; leaf blades shallowly and indistinctly lobed.   5 Boykinia rotundifolia
4 (2) Hypanthia saucer-shaped; petals suborbiculate to ovate, base contracted to claw, margins undulate.   3 Boykinia major
+ Hypanthia campanulate to turbinate; petals ovate to spatulate, base tapered to claw, margins plane   (5)
5 (4) Rhizomes usually underground, not usually stoloniferous; stipules of cauline leaves usually expansions from petiole base, fringed with brown hairs, sometimes foliaceous; nectaries green.   1 Boykinia aconitifolia
+ Rhizomes proliferating above ground, stoloniferous; stipules of cauline leaves usually foliaceous; nectaries greenish yellow.   2 Boykinia intermedia

Lower Taxa


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