Petalonyx
Petalonyx thurberi
sandpaper-plant
sandpaper plant, Thurber's sandpaper plant
erect or spreading.
cauline;
petiole present or absent;
blade ovate, elliptic, lanceolate, or falcate, unlobed, margins dentate, serrate, crenate, or entire.
petiole absent;
blade ovate to elliptic, with marked size dimorphism, to 45 × 15 mm, much larger on main stems than on fertile branches, base acute to rounded, margins usually serrate or crenate, distal often entire, apex acute.
racemes or panicles;
peduncle inconspicuous.
to 40-flowered.
not elongating in fruit.
hypanthium adnate to ovary proximally, free distally;
perianth whorls differentiated;
sepals green, connate basally, lanceolate, shorter than petals;
petals white, distinct or connate, spatulate or obovate, erect proximally, spreading to divaricate distally (corolla salverform or appearing so), glabrous except hairy abaxially on midribs;
nectary distal on ovary;
stamens 5, exserted, filaments monomorphic, filiform, longer than anthers;
anthers without distal connective extension;
staminodes absent [present];
pistil pseudomonomerous, placenta subapical;
stigma lingulate, 2-lobed, papillate.
conspicuously bilaterally symmetric;
petals spatulate, to 6.5 mm, claws postgenitally distally coherent, forming slitted corolla tube;
stamens exserted laterally through slits between petal claws.
cypselae, ±clavate, straight;
sepals persistent.
1, ovoid.
= 23.
= 46.
Petalonyx
Petalonyx thurberi
Species 5 (4 in the flora).
Petalonyx belongs to subfam. Gronovioideae, which is characterized by relatively small flowers that have five stamens, one ovule, and indehiscent fruits. Petalonyx is most closely related to a clade that consists of Cevallia, Fuertesia Urban, and Gronovia Linnaeus (L. Hufford et al. 2003). Petalonyx crenatus A. Gray ex S. Watson, from Coahuila, Mexico, is the only species of the genus known only from outside the flora area; it can be distinguished from the species treated here by having two anther-bearing stamens and three shorter staminodes, rather than having five anther-bearing stamens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Subspecies 2 (2 in the flora).
W. S. Davis and H. J. Thompson (1967) called attention to geographical variation in Petalonyx thurberi and distinguished subsp. gilmanii, which is restricted to washes in Inyo County, California, from the widespread subsp. thurberi. Subspecies gilmanii has flowers on the small side of those found among other populations of P. thurberi, although floral attributes do not readily distinguish between the two named subspecies. Davis and Thompson also noted another form that has relatively small leaves on and closely appressed to the inflorescence-bearing stems, although they did not formally distinguish this variant with a name. Morphometric and phylogeographic studies are warranted in P. thurberi to test whether morphological variation is significant, geographically partitioned, and associated with genetically isolated lineages.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf blades usually elliptic, sometimes falcate, to 5 mm wide, margins entire; petal claws distinct; stamens exserted distally (not laterally between petal claws). | P. linearis |
1. Leaf blades ovate, or if elliptic then to 15–30 mm wide, margins usually serrate, dentate, or crenate, sometimes entire; petal claws postgenitally distally coherent; stamens exserted laterally through slits between petal claws. | → 2 |
2. Petioles absent; leaf blades with marked size dimorphism, much larger on main stems than on fertile branches; petals to 6.5 mm. | P. thurberi |
2. Petioles 0.5–4 mm; leaf blades without marked size dimorphism; petals 6–15 mm. | → 3 |
3. Inflorescences 10–30-flowered; petals 6–11 mm; branches of current season 11–37 cm. | P. nitidus |
3. Inflorescences 35–65-flowered; petals 10–15 mm; branches of current season to 13 cm. | P. parryi |
1. Hairs on inflorescence-bearing stems ± retrorse. | subsp. thurberi |
1. Hairs on inflorescence-bearing stems ± erect. | subsp. gilmanii |
CA
WildflowerSearch
iNaturalist
USDA Plants Database
