Adenocaulon Hook., 1829

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 : 7-9

Adenocaulon Hook., 1829 Figures 4 , 5

Adenocaulon Hook., Bot. Misc. 1: 19. 1829. TYPE: Adenocaulon bicolor Hook.

Etymology.

From the Greek aden, gland, and kaulos, stalk, stem, describing the stalked glandular hairs.

Description.

Herbs perennial, scapiform with stout rhizomes, stems simple, erect, with stipitate-glandular hairs. Leaves glabrous to subglabrous above, tomentose beneath; basal leaves rosulate to sub-rosulate; petiolate to pseudopetiolate; blades elliptic, ovate, obovate, to deltoid, margin entire to lyrate, pinnately to palmately veined; upper leaves similar to the basal ones but few and reduced. Inflorescence terminal, laxly racemose to corymbose, on long peduncles; heads pedunculate, heterogamous, disciform; receptacle epaleate; involucre uniseriate. Florets dimorphic; marginal florets female, without staminodes, corolla sub-bilabiate (3+1 corolla lips), tubular-funnelform 4- to 5-lobed, rarely bilabiate; central florets male with a rudimentary ovary, corolla tubular-funnelform, deeply 5-lobed; anther apical appendages rounded to acute at the apex, basally constricted and demarcated from the thecae, anthers light colored and basally auriculate with tails very short, smooth; style bilobed, branches dorsally papillose. Achene truncate at the apex, pubescent (glandular multiseriate capitate hairs), dimorphic, marginal achenes conspicuously bigger than the central ones; pappus absent. [modified from Katinas et al. 2008]

Pollen spheroidal, circular in polar view, medium size, P × E = (26-32 × 26-30) µm. Tricolporate, colpi long with thin margin and microgranulate membrane, mesoaperture diffuse. Exine Mutisia type, microechinate, 4-5 µm thick, slightly slender at the poles. Ratio ectosexine/endosexine: 1:1.5; 1:2. Nexine 1.5 µm thick. SEM: tectum punctate. Note: pollen of Adenocaulon bicolor was found to be identical to that of Adenocaulon chilense Less.

Habitat and distribution: Genus of five species with a disjunct distribution in Patagonia, Mesoamerica, northern United States and southern Canada, and temperate southeastern Asia (Fig. 3 ). Inhabits moist forests in the shade of Pinus spp., Quercus spp. and Nothofagus spp. ( Bittmann 1990a, b, and field observations). Details of the flower morphology, including the differences between the male and female flowers, can be found in Ayers (1900).

Species list:

five species falling into three morphological groups that are biogeographically distinct (according to Blake 1934):

Group A: North America and East Asia

1. Adenocaulon bicolor Hook., Bot. Misc. 1: 19. 1830. (British Colombia to south central California, eastward to Montana and sparingly to Michigan)

Adenocaulon integrifolium Nutt.

2. Adenocaulon himalaicum Edgew., Trans. Linn. Soc. London 20: 64. 1851. Himalayan region and Japan

Adenocaulon adhaerescens Maxim. (described from Japan)

3 Adenocaulon nepalense M. Bittmann, Candollea 45: 403. 1990. Nepal

Group B: Chiapas, Mexico & Guatemala

4. Adenocaulon lyratum S. F. Blake, J. Wash. Acad. Sci. 24: 435 1934.

Group C: South America

5. Adenocaulon chilense Less., Linnaea 6: 107. 1831. (Southern Chile and the Magellan region)

Adenocaulon lechleri Sch. Bip.

Figures

Figure 3. Map showing distribution of Eriachaenium and Adenocaulon.

Figure 4. Adenocaulon. A Habitat, understory of Nothofagus dominated forest (Araucania Region, Chile) B Habit C Close up of rosette, note the bullate leaves D Close up of heads; arrows indicate marginal florets, note the conspicuous glandular trichomes on peduncles and other parts of the inflorescence E Close up of fruiting head; note the same trichomes on fruits. (Photos by M. Bonifacino)

Figure 5. Adenocaulon (from Katinas 2000). A habit B head C involucral bract D-E marginal florets F central floret G central achene H marginal achene I upper part of style J stamen K achene hair multiseriate, capitate, glandular. (Adenocaulon chilense: A LP s. n. ex LPS 16554; B-D, F Cabrera et al. 23066 LP; G-H Ricardi et al. 1983 LP. Adenocaulon bicolor: E Hedgcock s. n. LP, I-K Morrison 121 LP)