Drosanthemopsis, Rauschert

Klak, C., Hanáček, P. & Bruyns, P. V., 2018, A recircumscription of Jacobsenia (Aizoaceae): Re-instating Drosanthemopsis, with two new quartz-endemics from Namaqualand, South Africa and sinking Knersia *, South African Journal of Botany 116 (10), pp. 67-81 : 77

5.2. Drosanthemopsis

Rauschert, Taxon 31(3): 555 (1982).

Type: Drosanthemopsis vaginata (L.Bolus) Rauschert.

Anisocalyx L.Bolus , Notes Mesembryanthemum 3: 385 (1958) non Hance ex Walpers, Bot. Syst. (Walpers) 3(2): 195 (1852), nom. illegit.

Type: Anisocalyx salarius L.Bolus.

Knersia H.E.K.Hartmann & Liede, Bradleya 31: 126 (2013), syn. nov.

Type: Knersia diversifolia H.E.K.Hartmann & Liede.

Succulent perennial caespitose shrublet, main stems erect to 150 (− 200) mm high or procumbent to 80 mm high, stems to 10 mm diam.; difference between long and short shoots distinct or indistinct. Leaves succulent, opposite, basally free or fused into a sheath, dirty green to reddish, rarely grey, ascending, trigonous to club-shaped, upper surface flattened, lower surface towards the apex distinctly keeled or keels indistinct to apically rounded, to 8–35 mm long and 4–11 mm diam., at least the last leaf-pair of the season persisting on the stem until the next season; leaf-pairs of a season isophyllous, basally free or connate for c. 1 / 5 of their length; epidermis with large bladder cells with thickened outer walls, cells 0.075 mm to 0.3 mm diam., ± circular to polygonal, bladder cells with flat top either covered with tiny protrusions on their surface or with many antler-like protrusions, especially along the margin. Flowers terminal, solitary, emerging from the connate portion of the 1st leaf-pair of the season, 32–40 mm diam., pedicels 6–23 mm long, sepals 6 (to 8), succulent, the two outer calyx lobes opposite and bigger than the inner four lobes, petaloid staminodes in 4 or 5 rows, pink or white or pink with white centre, inner petals shorter, filamentous staminodes very few or absent, filaments white or yellow, papillate at bases; nectary a crenulate ring; flowering July to September. Fruit a hygrochastic capsule, borderline between expanding keels and expanding sheets distinct; covering membranes covering more than ¾ of the locule, without additional closing devices below the covering membranes, closing bodies absent, present or infrequently formed, numerous sterile funicles in the upper part of the placenta, valve wings broad; locules 6–9(−16), 5–17 mm diam. Seeds with translucent testa or testa ochre to brown, testa minutely papillate, c. 0.7 × 0.5 mm.

Ecology and distribution: Four species endemic to South Africa, from south of Port Nolloth, Northern Cape, to the Clanwilliam district, Western Cape ( Fig. 6 ). In shallow rocky soils, in loamy often strongly saline ground, with a cover of quartz-gravel, mean annual precipitation of estimated 129 mm rainfall p.a. mainly from August to September ( Mucina et al., 2006).

Diagnostic characters: Drosanthemopsis shares many characteristics with Jacobsenia (see 5.1), which prompted Ihlenfeldt (1997) to include D. vaginata in Jacobsenia . Differences between the two genera are given in Table 1 . Certain epidermal characters in Drosanthemopsis are unique within the Aizoaceae ( Fig. 5 ).

5.2.1. Key to Drosanthemopsis :

1. Leaves bright or dirty green, often suffused with red, 8–18 mm long…...………………………..…..………….………………………………...2

1.’ Leaves grey, 23–35 (−40) mm long…………………… 4. D. vaginata

2. Erect to spreading, loosely branched shrubs; leaves 3–4 mm diam..…. ……………………..………………………………1. D. diversifolia

2.’ Plants compact; leaves 5–10 mm diam…………………………………3

3. Low, sprawling shrublets, 30–50 mm high; leaves light green, usually suffused with red; leaf-pairs basally shortly connate for <c. 1 / of their 5 length; fruits with 6 locules…………………………………. …. 2. D. bella

3.’ Erect, densely branched shrublets, 150 (−200) mm tall, to 200 mm diam.; leaves dirty green; leaf-pairs basally connate for c. ⅓ of their length; fruits with 7(8) locules……….………....…... 3. D. kwaganapensis

Figures

Fig. 6. Distribution of Drosanthemopsis and Knersia, with phytochoria indicated (Knersvlakte,Riethuis-Wallekraal, Southern Richtersveld).

Fig. 5. Scanning electron micrographs of the leaf epidermis found in the Drosanthemopsis clade.A. D.kwaganapensis, Klak 2379 (BOL),showing the conspicuous antler-like protrusions; B. D.vaginata, Klak 2311 (BOL),with antler-like protrusions similar to those found in D.kwaganapensis; C. D.bella, Klak 2309 (BOL),with fewer and smaller antler-like protrusions than found in A&B.D. D. diversifolia, Klak 883 (=Knersia diversifolia) (BOL).