Eriachaenium Sch. Bip.

Funk, Vicki A., Pasini, Eduardo, Bonifacino, J. Mauricio & Katinas, Liliana, 2016, Home at last: the enigmatic genera Eriachaenium and Adenocaulon (Compositae, Mutisioideae, Mutisieae, Adenocaulinae), PhytoKeys 60, pp. 1-19 : 7

Eriachaenium Sch. Bip. Figures 1 , 2

Eriachaenium Sch. Bip. Flora 38: 120. 1855. TYPE: Eriachaenium magellanicum Sch. Bip.

Etymology.

From the Greek erion, wool, and the Latin achaenium, a type of fruit, describing the villose fruits.

Description.

Herbs perennial, dwarf, with stout, oblique to vertical rhizomes that are compressed laterally, stems prostrate to ascending. Leaves alternate; sessile, clasping; blades oblanceolate, pinnately veined, margin entire to undulate-dentate, glabrous to subglabrous above, tomentose beneath. Inflorescence monocephalous, axillar; heads pedunculate, heterogamous, disciform; receptacle epaleate; involucre uniseriate. Florets dimorphic; marginal florets female with staminodes, corolla tubular-funnelform, deeply 4-lobed; central florets bisexual or male with a rudimentary ovary, corolla tubular-funnelform, deeply 5-lobed; anther apical appendages rounded to acute, basally constricted and demarcated from the thecae, anthers dark, basally auriculate with tails very short, smooth to slightly papillose; style bilobed, dorsally papillose. Achenes truncate at the apex, densely pubescent, dimorphic, the marginal achenes conspicuously bigger than the central ones; pappus absent. [modified from Katinas et al. 2008]

Pollen spheroidal to prolate, spheroidal or elliptic in equatorial view, circular in polar view, medium size, P × E = (30-36 × 24-30) µm. Tricolporate, colpi long with thin margin and microgranulate membrane, mesoaperture diffuse. Exine Mutisia type, microechinate, 2-6 µm thick, slightly slender at the poles. Ratio ectosexine/endosexine: 1:1.5; 1:2. Nexine 1.5 µm thick. SEM: tectum punctate.

Habitat and distribution. Genus with only one species, Eriachaenium magellanicum Sch. Bip., endemic to Patagonia in Argentina and Chile (Fig. 3 ). It grows in mud, sand, and pebbles either along the margins of inland somewhat saline lakes or near the coast in estuaries ( Morore 1983 and field observations).

Species list.

Eriachaenium magellanicum Sch. Bip., Flora 38: 121. 1855.

Figures

Figure 1. Eriachaenium. A General habitat, muddy shores of temporal lakes; central Chubut (Argentina) B Habit detail; notice stems adpressed to the ground C Lateral view of rhizome D Dorsal view of rhizome; compare with C and note the flattened nature of rhizome E Close up of leaves, note the bullate condition. F Detail of heads G Detail of heads; arrows point marginal florets. (Photos by M. Bonifacino)

Figure 2. Eriachaenium magellanicum (from Katinas 2000). A habit B head C involucral bract D marginal floret E marginal floret opened showing the staminodes F central floret G marginal achene H central achene I upper part of style J stamen K cypsela hair flagellate, filiform. (Eriachaenium magellanicum: A Biraben and Biraben 242 LP; B-F, I-K Sleumer 908 LP; G-H LP s. n. ex LPS 13745)

Figure 3. Map showing distribution of Eriachaenium and Adenocaulon.