Geissorhiza mellimontana Goldblatt & J.C.Manning, 2021

Goldblatt, P., Manning, J. C. & van der Walt, J. A., 2021, Geissorhiza mellimontana (Iridaceae: Crocoideae), a new species from southwestern Western Cape, South Africa, South African Journal of Botany 139, pp. 197-199 : 198-199

Geissorhiza mellimontana Goldblatt & J.C.Manning , sp. nov.

Type: South Africa, Western Cape, Cape Town (3318): Heuningberg, west of Saron , (—BD), 29 July 2020, A. van der Walt sub J. Manning s.n. ( NBG, holo.; MO, iso.) .

Plants slender, 300—450 mm high. Corm ± ovoid, 8—12 mm diam. (larger when old tunic layers accumulated); tunics woody, brown, imbricate, outer layers notched below into truncate segments, drawn into bristles above. Stem erect, flexed at base of spike, with membranous, green bract 10—12 mm long in upper 1/4, simple. Leaves 2, basal, lowermost free from base, straight to falcate, cross-shaped in section, with strongly raised margins and midrib, thus with 4 grooves, ± 2 mm diam., sticky, often with adhering sand especially below, upper leaf sheathing almost entirely, enclosing stem in lower two thirds or nearly to base of spike, free part 10—30 mm long. Spike 5- to 8-flowered; bracts green, becoming dry, transparent and pale or rarely brownish above, spreading distally, 6—8 mm long, inner bract shorter than outer. Flowers actinomorphic, rotate, blue to lilac with white centre, usually darker around pale centre, perianth tube funnel-shaped, 1.0— 1.5 mm long; tepals narrowly elliptic, 12—14 X 3—4 mm. Filaments erect, unequal, 8—9 mm long, with one 1 mm shorter; anthers 3—4 mm, purple; pollen lilac. Style 10—12 mm long, dividing nearly opposite anther tips, branches 1.5—2.0 mm long. Capsules unknown. Chromosome number unknown. Flowering time: late July to early August Fig. 1 .

Distribution and ecology: a local endemic of the Heuningberg, an isolated sandstone hill west of Saron in Western Cape, South Africa ( Fig. 2 ); on stony sandstone plateau in fynbos.

Diagnosis: Geissorhiza mellimontana is evidently closely allied to the more widespread G. scillaris , the two species sharing imbricate corm tunics and a distinctive vegetative morphology, with just two foliage leaves, the lower with a long, free blade and the upper sheathing the stem for most of its length, plus an inconspicuous green, sheathing bract inserted in the upper part of the stem a short distance below the spike (see Goldblatt, 1985: Fig. 57 for illustration). The blade of the lowermost leaf is terete with heavily thickened margins and main vein, thus cross-shaped in section with 4 longitudinal grooves. Both sheath and blade are sticky and usually have sand adhering to the surface. The two species, however, differ markedly in the size, and to some extent the flower colouring Table 1 .

Geissorhiza mellimontana is generally a larger plant with larger, lilac flowers, usually with a dark flush around the white centre, the flowers with much longer and relatively narrower, narrowly elliptic tepals 12—14 mm long, similarly unequal stamens but with much longer filaments 8—9 mm long, and a longer style 10—12 mm long. It is evidently an early-flowering species, in bloom from late July to early August, and known only from an isolated sandstone outcrop west of the range of G. scillaris and at lower altitude.

Geissorhiza scillaris is consistent throughout its range in its small, white to clear blue flowers with a white centre, elliptic tepals 7—9 mm long, and slightly unequal stamens with filaments 2—4 mm long and white anthers, and relatively short style 5—6 mm long. Careful examination of several well preserved flowers of G. scillaris confirms that the stamens are indeed slightly unequal, with one filament about 1 mm shorter than the others, this contrary to past published descriptions. It is largely a montane species, extending through the mountains of Western Cape, South Africa, from Pakhuis Pass and the Cederberg in the north to Shaw’ s Mtns in the Caledon District in the south, usually above 500 m elevation, and flowering from mid-August to October (or later at high elevations).

Etymology: Geissorhiza mellimontana is named for its only known locality on the Heuningberg [Afrikaans for Honey Mountain] (mellis = honey, montana = mountain) and brings to 105 the number of species recognised in the genus.

Conservation notes: Geissorhiza mellimontana is known from a single small population. We have no information on the size of the population but there are no evident threats as the soil is too rocky for cultivation. We therefore propose a conservation status of Critically Rare (known from a restricted area but without any potential threat).

Figures

Fig. 1. Geissorhiza mellimontana. Western Cape, Heuningberg, van der Walt sub Manning s.n. (NBG). A, Whole plant; B, Corm, showing imbricate tunics; C, Flowers, showing narrow tepals, long unequal filaments with purple anthers, and long style. Photographs: J.A. van der Walt (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.).

Fig. 2. Distribution of Geissorhiza mellimontana (•) and G. scillaris (O).