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Vascular Plants of California
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Hesperevax acaulis var. ambusticola

Higher Taxonomy
Family: Asteraceae (Compositae)View DescriptionDichotomous Key
Habit: Annual to tree. Leaf: basal and/or cauline, alternate, opposite, rarely whorled, simple to 2+ × compound. Inflorescence: 1° inflorescence a head, resembling a flower, of several types (see below), 1--many in generally +- cyme-like cluster; each head generally with +- calyx-like involucre of 1--many series of phyllaries (involucre bracts); receptacle of head flat to conic or columnar, paleate (bearing paleae = receptacle bracts) or epaleate; flowers 1--many per head. Flower: bisexual, unisexual, or sterile, +- small, of several types (see below); calyx 0 or modified into +- persistent pappus of bristles, scales, and/or awns; corolla radial or bilateral (0), lobes generally (0)3--5; stamens 4--5, filaments generally free, generally fused to corolla at tube/throat junction, anthers generally fused into cylinder around style, anther base generally rounded or cordate (deeply sagittate or with tail-like appendages), tip (= flattened appendage) generally projecting beyond pollen sac; pistil 1, 2-carpeled, ovary inferior, 1-chambered, 1-seeded, placenta basal, style 1, tip generally +- 2-branched (except in some staminate disk flowers), branch tips truncate or generally bearing +- brush-like appendages; stigmas 2, generally on adaxial faces of style branches. Fruit: achene (also called a cypsela) (drupe in Chrysanthemoides), cylindric to ovoid, sometimes compressed, generally deciduous with pappus attached.
Genera In Family: +- 1500 genera, 23000 species: worldwide, many habitats. Note: Flower and head types differ in form and sexual condition. A disk flower has a generally radial corolla, with a cylindric tube, expanded throat, and generally 5 lobes. Disk flowers are generally bisexual and fertile but occasionally staminate with reduced ovaries. Discoid heads comprise only disk flowers. A radiant head is a variant of a discoid head, with peripheral disk flower corollas expanded, often bilateral. A ray flower corolla is bilateral, generally with a slender tube and flattened petal-like ray (single lip composed of generally 3 lobes). Ray flowers are generally pistillate or sterile (occasionally lacking styles). Radiate heads have peripheral ray flowers and central disk flowers. Disciform heads superficially resemble discoid heads, with pistillate or sterile flowers that lack rays, together with or separate from disk flowers. A ligulate flower is bisexual, with a bilateral, generally ephemeral corolla and 5-lobed ligule. Liguliflorous heads comprise only ligulate flowers. See glossary p. 31 for illustrations of family characteristics. Echinops sphaerocephalus L., Gaillardia aristata Pursh, Gaillardia pulchella Foug., Hymenothrix loomisii S.F. Blake, Tagetes erecta L., Thelesperma megapotamicum (Spreng.) Kuntze are waifs. Melampodium perfoliatum Kunth, historic urban waif. Ageratum conyzoides L., Guizotia abyssinica (L. f.) Cass., Santolina chamaecyparisus L., orth. var. are rare or uncommon escapes from cultivation. Dyssodia papposa, Ismelia carinata (Schousb.) Sch. Bip. [Chrysanthemum carinatum Schousb.], Mantisalca salmantica (L.) Briq. & Cavill. are historical or extirpated waifs in California. Inula helenium L. not documented in California. Taxa of Aster in TJM (1993) treated here in Almutaster, Eucephalus, Eurybia, Ionactis, Oreostemma, Sericocarpus, Symphyotrichum; Chamomilla in Matricaria; Bahia in Hymenothrix; Cnicus in Centaurea; Conyza in Erigeron and Laennecia; Dugaldia in Hymenoxys; Erechtites in Senecio; Hymenoclea in Ambrosia; Lembertia in Monolopia; Osteospermum ecklonis in Dimorphotheca; Picris echioides in Helminthotheca; Prionopsis in Grindelia; Raillardiopsis in Anisocarpus and Carlquistia; Schkuhria multiflora in Picradeniopsis; Trimorpha in Erigeron; Venidium in Arctotis; Whitneya in Arnica. Amauriopsis in TJM2 (2012) treated here in Hymenothrix; Arida in Leucosyris; Bahia in Picradeniopsis.
Unabridged Note: Largest family of vascular plants in California and of eudicots globally.
eFlora Treatment Author: David J. Keil, except as noted
Scientific Editor: David J. Keil, Bruce G. Baldwin.
Genus: HesperevaxView DescriptionDichotomous Key

Habit: Annual 0.5--10(20 cm), +- green to gray, woolly to cobwebby. Stem: 0, or 1, erect, or 2--10, +- decumbent to ascending, generally unbranched or branched proximally, equally or more leafy distally. Leaf: alternate, sessile or petioled, oblanceolate to spoon-shaped, entire, base +- yellow, +- hard; distal leaves subtending heads, +- crowded, largest >= proximal leaves. Inflorescence: heads disciform, sessile, single or 2--40+ per group; involucre 0, simulated by paleae or leaves; receptacle length 0.8--1.3 or 4--6 × width, +- conic, acuminate, bristly; paleae of pistillate flowers open, lanceolate to obovate, acute, flat to concave or +- folded, persistent, +- glabrous, obscurely parallel-veined, veins 5+, margin +- continuous, thinned but scarcely winged; paleae of disk flowers generally 5, +- enlarged, erect proximally, erect to spreading distally, open, obovate, obtuse, cartilaginous, proximally +- yellow, distally green and tomentose adaxially. Pistillate Flower: (3)5--25, all subtended by paleae; corolla obscure, narrowly cylindric. Disk Flower: staminate, 2--6(12); pappus 0; corolla (3)4(5)-lobed, +- bilateral; anther base tailed, tip +- triangular; style tips +- linear-oblong; pappus 0. Fruit: falling free of paleae, +- obovoid, compressed front-to-back, smooth, dull to +- shiny, corolla scar terminal; pappus 0.
Species In Genus: 3 species: western California, southern Oregon. Etymology: (Greek: western Evax) Note: Apparent sister of Ancistrocarphus; bristly receptacle unique. Historical California specimens of Diaperia [Evax sect. Diaperia], native central Arizona and eastward, are likely label errors.
eFlora Treatment Author: James D. Morefield
Reference: Morefield 2006 FNANM 19:467--470
Unabridged Reference: Morefield 1992 Syst Bot 17:293--310
Species: Hesperevax acaulisView Description 

Common Name: DWARF EVAX
Stem: 0 or 1--10, prostrate to erect, to 7 cm. Leaf: distal > proximal, longest 4--22(32) mm, < 5 mm wide; petiole 0--1.5 × blade, base scarcely thickened. Inflorescence: distal heads generally 1, terminal, 2--4 mm, 1.5--3.5 mm wide, +- bell-shaped, length 1--1.5 × width, subtended by generally 6--12 leaves (in varieties acaulis and robustior distal heads rarely 2--8 per group, largest group dense, 3--7 mm wide, mixed with leaves); proximal heads 0 or axillary, < distal; receptacle length 1--1.3 × width; paleae in spiral ranks; paleae of disk flowers 0.6--0.8 × head, tips exserted, spreading. Disk Flower: 0.6--1 mm. Fruit: 0.6--1.6 mm.
Note: Varieties intergrade.
Unabridged Note: Butte, Tehama cos. reports of Hesperevax acaulis var. acaulis, Hesperevax acaulis var. ambusticola await confirmation.
Hesperevax acaulis var. ambusticola Morefield
Habit: Plants 0.5--2(4) cm. Stem: (0)4--10, +- prostrate (when depauperate 0 or 1, erect, unbranched); branches proximal and/or distal. Leaf: largest generally 4--7 mm, 1--2 mm wide, distal generally spreading; petiole generally 0.5--1.5 × blade; blade obovate to round, obtuse. Inflorescence: distal heads 2--2.5 mm, 1.5--2 mm wide; receptacle 1--1.4 mm; paleae of pistillate flowers generally in 2--3 series, 1.7--2.5 mm; longest paleae of disk flowers 1.6--2 mm. Fruit: generally 0.8--1 mm.
Ecology: Clearings, barren slopes, burns; Elevation: 200--1300 m. Bioregional Distribution: s NCoRI, n&c SNF, s SNH, sw SnJV, e SnFrB, SCoR, SnGb/SCo, nw PR (exc SnJt). Flowering Time: Apr--Jun Note: Depauperate plants among smallest Asteraceae.
Jepson eFlora Author: James D. Morefield
Reference: Morefield 2006 FNANM 19:467--470
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Botanical illustration including Hesperevax acaulis var. ambusticola

botanical illustration including Hesperevax acaulis var. ambusticola


Citation for this treatment: James D. Morefield 2012, Hesperevax acaulis var. ambusticola, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on October 14, 2019.

Citation for the whole project: Jepson Flora Project (eds.) 2019, Jepson eFlora,, accessed on October 14, 2019.

Hesperevax acaulis var. ambusticola
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© 2012 Aaron Schusteff
Hesperevax acaulis var. ambusticola
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© 2004 Aaron Schusteff
Hesperevax acaulis var. ambusticola
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© 2010 Barry Breckling
Hesperevax acaulis var. ambusticola
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© 2010 Barry Breckling
Hesperevax acaulis var. ambusticola
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© 2004 Keir Morse
Hesperevax acaulis var. ambusticola
click for enlargement
© 2004 Keir Morse

More photos of Hesperevax acaulis var. ambusticola in CalPhotos

Geographic subdivisions for Hesperevax acaulis var. ambusticola:
s NCoRI, n&c SNF, s SNH, sw SnJV, e SnFrB, SCoR, SnGb/SCo, nw PR (exc SnJt).
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Data provided by the participants of the  Consortium of California Herbaria.
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CCH collections by month

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Blue line denotes eFlora flowering time.