Tristagma Poeppig (1833: 8)

Arroyo-Leuenberger, Silvia C. & Sassone, Agostina B., 2016, An annotated checklist of the genus Tristagma (Amaryllidaceae, Allioideae), Phytotaxa 277 (1), pp. 21-35 : 22

Tristagma Poeppig (1833: 8) . Type species:— Tristagma nivale Poepp.

= Steinmannia Phil (1884: 64) ≡ Garaventia Looser (1944: 79) . Type species:— Steinmannia graminifolia Phil.

- Gardinia Bertero (1829: 643) nom. nud.

Perennial herbs, 10–31(–45) cm tall. Roots fibrous. Bulb indeterminate, tunicate, simple, without conspicuous alliaceous odour. Leaves few, eligulate, linear, green, glabrous; leaf sheaths forming a subterranean neck. Scapes 1–2(–4), lateral, subcylindric, glabrous. Inflorescence an umbellate cyme (1–)2 or multiflowered. Spathe formed by 2 bracts, fused at the base, cylindric, membranous-papery, plurinerved; pedicels cylindric, glabrous, not articulated, in some species it recurves after anthesis. Flowers bisexual, hypogynous, trimerous, actinomorphic, white, yellowish, greenish, purple, sometimes dark purple dark, grey or dark-brown. Perigone persistent, tepals 6, fused, forming a conspicuous tube around the ovary; free part of tepals patent or circinate. Stamens 6, always disposed in two series; staminal filaments free, linear sometimes slightly awl-shaped, always fused to the tepal tube; anthers linear, greenish-yellow, dorsifixed. Ovary sessile, oblong, 3-carpellate, septal nectaries present, ovules arranged in 2 rows, style subtrigonous, stigma capitate, 3-lobate to 3-fid. Capsule aerocarpic, globose, multiseeded. Seeds poliedric; tegument black. Chromosome number x = 4 ( Crosa 1981, Souza 2012).

Etymology: — From Greek tri = three; stagma = that which drips, hence nectary ( Stearn 1973). Poeppig (1833) and Muñoz-Schick et al. (2012) described three nectar drops exuded from the ovary.

Distribution: — In Argentina the genus is distributed from Mendoza to the Patagonian region and more widely in Chile, from Patagonian area to Coquimbo region, in the Andes and Cordillera de La Costa, and also inhabits the coast from Bio Bio to Coquimbo (Figs. 1, 2). According to Ravenna (2005a), Tristagma reaches Cuzco ( Peru) but no material was found for this area (see: Doubtful species).

Habitat: — Tristagma species occur in open areas, grassland, Patagonian Andean forest, lowlands, gentle slopes or mountain areas (Cordillera de los Andes) with rocky or sandy soil. Some species grow at sea level [e.g. T. gracile (Fig. 1E), T. porrifolium ( Fig. 2D )] and others in high mountain areas [e.g. T. bivalve (Fig. 1C), T. circinatum (Fig. 1D)]. Three species are distributed from sea level up to 2500 m.a.s.l.: T. ameghinoi (Fig. 1A), T. nivale ( Fig. 2B ) and T. patagonicum ( Fig. 2C ).

Phenology: — Tristagma species flower from July to February.

Note: — Ravenna (2001) divided Tristagma into three sections: T. sect. Tristagma , T. sect. Ipheion (Raf.) Ravenna (2001: 31) and T. sect. Nivella Ravenna (2001: 31) . Until more phylogenetic studies are available we prefer not to recognize any subgeneric division.

Figures

FIGURE 2. Area of distribution of: A, T. graminifolium. B, T. nivale. C, T. patagonicum. D, T. porrifolium. E, T. violaceum.