Three new species of Diascia (Scrophulariaceae) from the Western Cape, South Africa

Three new annual species o f Diascia Link & Otto are described from the Western Cape Province o f South Africa. D. collina is characterized by greyish magenta flowers with two divergent yellow sacs containing oil-secreting trichomes. It is restricted to granite outcrops in the vicinity o f Saldanha Bay, from the West Coast National Park and Langebaan north to Vredenburg. D. pusilla is closely related to D. collina. but differs from that species in having smaller flowers with shorter, ± parallel sacs, and posticous filaments that lack a protuberance where they bend sharply backwards towards the upper lip. It occurs in grey to whitish sands usually near seasonally moist or wet areas. It has not been found more than 35 km from the coast and ranges from Modderrivier, south o f Darling, north to Lambert’s Bay. D. appendiculata is related to D. diffusa (Thunb.) Benth. and is characterized by having small, mainly reddish lilac to greyish magenta flowers, two shallow depres­ sions in the corolla tube at the base of the upper lip, and posticous filaments with sterile appendages. It is known from only six localities in the general vicinity of Citrusdal and occurs in fynbos vegetation on lower mountain slopes or flats, in loose alluvial sands derived from Table Mountain Sandstone.


INTRODUCTION
Diascia Link & Otto is a genus of ± 72 species of annual and perennial herbs endemic to southern Africa. Two sections have been recognized, section Racemosae with 27 species and section Diascia with about 45 spe cies (Hilliard & Burtt 1984;Steiner unpubl.). Section Racemosae was revised by Hilliard & Burtt (1984) and three additional taxa were described more recently (Steiner 1989(Steiner , 1999. Section Diascia has not been revised since Hiem's (1904) treatment in Flora capensis, although many new species have been described in recent years as part of a revisionary study (Steiner 1992a(Steiner , b, c, d 1995. Section Diascia consists solely o f annual species, whereas section Racemosae is mostly perennial (81 %). Three additional new species in Section Diascia from the Western Cape are described here. All descriptions are based on living material collected from the field. Flower colours are based on the Methuen handbook o f colour (Komerup & Wanscher 1984). Chromosome counts of these species were reported by Steiner (1996).
Diagnostic features: Diascia collina is most similar to D. pusilla, but it differs from that species in having a larger corolla (13.3-23.0 * 14.3-26.0 mm vs 9.1-13.5 x 9.0-14.3 mm), longer corolla sacs (4-5 mm vs 2.2-2.5 mm long) and a protuberance from the posticous fila ments where they bend backwards (Figure 1). D. collina is also similar to D. capensis (L.) Britten, but differs from that species in having stamens that are ± half the size and backwards-bending, rather than forward-arching. D. collina also has a shorter style (1.3-2.0 mm vs 3.5-5.2 mm) that is less curved, and corolla sacs that are strongly divergent, not ± parallel like those of D. capensis.
Diagnostic features: Diascia pusilla differs from its nearest relative, D. collina, in corolla size, shape oi the posticous filaments, size and shape o f the corolla sacs, and habitat. The difference in flower size between the two taxa is not simply a function of plant vigour, since small plants of D. collina at Postberg, with only a few leaves, have much larger flowers than robust plants of D. pusilla, with many large leaves and long thick stems, at Droogerivicr. Corolla limb length of D. pusilla reaches 13.5 mm, but averages 11.5 mm, whereas limb length of D. collina ranges from 13.3 to 23 mm, but averages 17 mm. The corolla sacs of D. pusilla are about half the size o f D. collina sacs (2.1 mm vs 4.4 mm long) and are par allel or only slightly divergent near the tips. They are not strongly divergent like those of D. collina. The shapes of the filaments also differ between these two species. D. pusilla lacks the protuberance on each posticous filament that is present in D. collina.
Etymology: the name refers to the small size o f the flowers.
Distribution and habitat: Diascia pusilla is known from a narrow strip along the Cape west coast, from the Farm Modderrivier (Mud River) (southwest of Darling), north to Lambert's Bay and as far east as Droogerivier (± 4.5 km SE of Sandberg). It occurs no more than 35 km from the sea and ranges in elevation from sea level to nearly 100 m (Figure 2). On the farms Droogerivier and Suurfontein (near Lambert's Bay), it occurs in or near riverine or vlei systems, often in poorly drained, seasonally wet sands, but in other localities, the habitat is drier. In all cases, it occurs in loose white to greyish sands. Southwest of Darling it has been reported from short fynbos in deep sand (Hugo 2427). It does not occur in areas with granitic outcrops, typical of D. collina. Pollination and breeding system: like most Diascia species, D. pusilla has oil-secreting glands in its corolla sacs. Unlike D. collina, this species is facultatively auto gamous and, therefore, does not need visits by oil-col lecting bees to set seed. At the type locality, and at least one other locality, D. pusilla occurs and flowers concur rently with Hemimeris racemosa (Scrophulariaceae), another oil-secreting species. Since at both these sites oil-collecting bees have been caught on H. racemosa, it is probable that these same bees visit D. pusilla. At the type locality, Droogerivier, and at Kerscfontein, D. pusilla occurs with Rediviva parva (Whitehead & Steiner 2001). Annual herb, rosulate, glabrous, sim ple or branch ing from base. Stents decumbent, up to 220 mm long, angular, up to 6-sided, ribs 2 or m ore, sides up to 2 mm wide. Leaves simple, alternate, opposite or whorled, petiolate, erect or spreading; lam ina mostly oblong, but also ovate to obovate, 9-35 x 3 -9 mm, apex acute to rounded, base attenuate; m argins sinu ate, pinnatipartite or pinnatisect, lobes up to ± 5 mm long, ovate, obovate, oblong or deltoid, apices rounded to acute; petioles up to ± 15 mm long; cauline leaves progressively smaller upwards. Flowers axillary, 1 or 2 open flowers per stem, nodding in bud, long pedicelate; pedicels 17-53 mm long, ascending, dorsiventrally flattened especially where attached to flower, elongating and spreading at right angles to stem in fruit, with an abrupt downward curve 3-4 mm from base o f developing capsule. Calyx lobes 5, spreading, lanceolate, acuminate, margins white-ciliate, upper 3 segments ± equal, 2.4-3.1 x 1.0-1.6 m m , lower 2 segments slightly wider. Corolla bilabiate, 5-lobed, limb 7.4-14.3 x 7.7-14.8 mm; upper lobes ovate to obovate, 2.0-4.7 x 2.5-5.2 mm, outer sides longer than inner sides, apices rounded to em arginate, bases oblique; lateral lobes oblong-ovate, 2 .5 -4 .6 x 2.8-4.6 mm, sides ± equal in length, apices rounded to emar ginate, lower lobe obcordate, 3.1-5.0 x 3.6-6.4 mm, all lobes reddish lilac (14C4) to greyish magenta (14D6) on inner surface and violet-white to purplish white on reverse side, with scattered black or clear glandular trichomes on both sides; tube shallowly cupped, dark ruby to violet-brown, very shallowly bisaccate, sacs or depressions 0.3-1.0 x 1.0-1.6 mm, 0.5-0.7 mm deep, yellow, oil-secreting trichomes clustered within; central stamen-bearing boss oblique, sparsely glandular pubescent, anticous portion 0.5-1.0 mm high, ruby, posticous portion ± 2.0 mm high, yel low. Stamens 4, erect from the boss; filaments ruby, usually glabrous, occasionally covered with dark pur ple, clavate trichomes; anticous filaments (twisted at the base and appearing posticous) ± straight, 2.1-2.5 mm long, base strongly curved; posticous filaments ± 2.3 mm long, with sterile appendages, ± 0.8 mm from base, appendages 0.1-0.8 mm long, sometimes reduced in length to a small nub, filament above bend ± 1.5 mm long; anthers 0.3 mm long, strongly coher ing, greenish yellow; pollen orange. Ovary ovoid, lat erally compressed contrary to septum, 1.2-1.5 x ().8-1.1 mm, falciform; ovules 27-47; style ± 1.2 mm long, /9ea  Diagnostic features: Diascia appendiculata is most closely allied to D. diffusa. Both species have posticous filaments with sterile appendages, but the stamens are erect in D. appendiculata and projecting forward in D. diffusa. Furthermore, the filaments in D. appendiculata are usually glabrous, whereas those of D. diffusa have clavate trichomes. Both species also have two localized patches o f oil-secreting trichomes, but in D. diffusa they are clustered in two short, but distinct, spurs (at the base of the upper corolla lip), whereas in D. appendiculata they are present in two shallow, yellow depressions that may or may not be visible on the outside o f the corolla as a slight swelling of the tube.

Other specimens examined
Etymology: the name refers to the filament appendages.
Distribution and habitat: Diascia appendiculata is known from only six localities in the general vicinity of Citrusdal (Figure 2). It occurs between elevations of 100 to 300 m in fynbos vegetation on lower mountain slopes or flats in loose alluvial sands derived from Table  Mountain Sandstone. In five of the localities it occurred on first year bums, while in the other locality it was col lected from a roadside area next to cultivated land at the northeastern base of the Piketberg. On Grey's Pass, it was most abundant in the first season after fire, but was also observed in the second and third years (1990,1991) after fire. It could not be found in the fifth and sixth years. The stimulation of germination in response to fire is also found in other Diascia species such as D. elongata Benth. and D. maculata K.E.Steiner. Pollination and breeding system: Diascia appendicu lata is facultatively autogamous. However, because it secretes floral oil, it is probably visited and cross-pollinated, at least occasionally, by small oil-collecting Rediviva bees (Melittidae) such as R. parva Whitehead & Steiner, R. intermixta (Cockerell) or R. aurata White head & Steiner (Whitehead & Steiner 2001).