7. Acanthoscyphus Small, Bull. Torrey Bot. Club. 25: 53. 1898.
Flowery puncturebract [Greek acantha, thorn, and scyphos, cup, alluding to awn on involucre]
James L. Reveal
Oxytheca Nuttall sect. Acanthoscyphus (Small) Ertter
Herbs, annual; taproot slender. Stems arising directly from the root, erect to somewhat spreading, solid, not fistulose or disarticulating into ringlike segments, glabrous, partially glandular. Leaves usually persistent through anthesis, basal, rosulate; petiole indistinct; blade broadly obovate or spatulate to oblong or oblanceolate, margins ciliate-denticulate. Inflorescences terminal, cymose; branches dichotomous, not brittle or disarticulating into segments, round, glabrous except for glandular nodes and proximal 2 of internode; bracts 2-3, connate basally, scalelike, triangular to lanceolate or subulate, awned at proximal nodes, glabrous or sparsely glandular. Peduncles erect to deflexed. Involucres 1 per node, not ribbed, tubular, turbinate; teeth 4(-5) or 7-30(-36), 1/ 2 to completely connate, awn-tipped, glandular distally adaxially. Flowers 3-10(-20) per involucre at any single time during full anthesis; perianth white to rose, occasionally greenish white to cream, broadly campanulate when open, narrowly urceolate when closed, hirsute to strigose and sparsely glandular abaxially; tepals 6, connate 4- 3 their length, monomorphic, entire or rarely irregularly divided apically; stamens 9; filaments basally adnate, glabrous or sparsely pubescent basally; anthers red to maroon, oblong to oval. Achenes usually included, dark brown to deep maroon, not winged, globose-lenticular, glabrous. Seeds: embryo curved. x = 20.
Species 1: s California.
Acanthoscyphus is allied to Eriogonum subg. Ganysma, specifically to E. parishii, E. apiculatum, and their close relatives. It is distinguished from Eriogonum by its awned involucres.
Ertter, B. 1980. A revision of the genus Oxytheca (Polygonaceae). Brittonia 32: 70-102.