A New Species of Galaxia (Iridaceae subfamily Iridoideae) from Namaqualand, South Africa

Abstract

Galaxia fenestralis is new a species from central interior Namaqualand, Cape Province, South Africa. Apparently most closely related to another Namaqualand endemic, G. kamiesmontana Goldblatt, G.fenestralis is distinguished by its terete, succulent leaves, and small light pink to mauve or whitish flowers with a yellow center and narrowly clawed tepals. It grows on exposed granite outcrops in virtually no soil, and flowers early in the rainy season, in June and July, a few weeks after the first of the season's rains have fallen. Comprising some 15 species, including the one described here, Galaxia Thunberg is restricted to the winter rainfall region of the southern and western Cape Province, South Africa (Goldblatt 1979a; 1984). A member of subfamily Iridoideae tribe Irideae (Goldblatt, 1991), Galaxia is distinguished from the related genera Moraea Miller and Homeria Ventenat by the absence of an aerial stem and by the cup-shaped flowers borne above the basal cluster of leaves on a short closed perianth tube. Two subgenera are currently recognized in Galaxia (Goldblatt, 1979a). Subgenus Galaxia comprises species with yellow or white flowers and apomorphic style lobes that are deeply and regularly fringed. In subgenus Eurystigma the flowers may be yellow but are more often pink to purple or reddish (also sometimes white), and the style lobes have entire margins, the plesiomorphic state. The new species, G. fenestralis (Figure 1), clearly accords with subgenus Eurystigma both in flower color and stigma features. Its flowers resemble most closely those of the only other Namaqualand member of the subgenus, G. kamiesmontana Goldblatt, in their pale pink to mauve color with a yellow center, small size, and in the rather narrowly clawed tepals. In other species of the subgenus the distinction between tepal limb and claw is obscure if present at all, and the flowers are considerably larger. NOVON 3: 404-407. 1993. Cytologically, subgenus Eurystigma is notable for a descending dysploid series. The presumed ancestral basic chromosome number for Galaxia is x = 9 (Goldblatt, 1979b, 1984), also the base number for all species of subgenus Galaxia and for G. kamiesmontana. Other species of subgenus Eurystigma have n = 8, 7, or 6. Unfortunately, chromosome number has not been determined for the new species, the only member of the genus for which this information is unknown. Galaxia fenestralis is distinguished by apomorphic nearly terete and succulent leaves with an adaxial band of transparent tissue (Fig. 2A). It is also unique in the genus in having the inner whorl of tepals connate for 2 mm with the filament column (Fig. 1B). Nectaries are present at the base of the outer tepals and can be recognized by their crescent shape and maroon edges (Figure 1 B). Nectaries have not been described in other species of Galaxia (Goldblatt, 1979a), but perigonal nectaries are typical of tribe Irideae (Goldblatt, 1990) where they commonly occur at the base of the outer tepals, as in Moraea and Iris (Goldblatt, 1991), or also at the base of the inner tepals. The short-lived flowers, which last from mid-morning when they open until about 3:30 PM, are typical of the genus. Such fugacious flowers are plesiomorphic for subtribe Homeriinae, to which Moraea and Homeria also belong (Goldblatt, 1990, 1991). The unusual leaves of Galaxiafenestralis (Figure 2A) are interesting anatomically. Although nearly terete, they are not centric. The peculiar transparent band on the upper leaf surface lacks chlorenchyma and is continuous with the cortical mesophyll, which is compact and lacks intercellular air spaces, which renders the leaf succulent. The window is bordered by single strands of subepidermal sclerenchyma fibers three cell layers thick. Elsewhere the epidermis overlies a palisade mostly of 3 cell layers. The outer walls of the epidermal cells are microThis content downloaded from 157.55.39.124 on Sat, 23 Jul 2016 04:55:44 UTC All use subject to http://about.jstor.org/terms Volume 3, Number 4 1993 Goldblatt & Oliver