TABLE 1. Prominent morphological differences between Petalidium karasbergense, P in Petalidium karasbergense (Acanthaceae), a new species from Namibia

TABLE 1. Prominent morphological differences between Petalidium karasbergense, P. parvifolium, and P. lucens.
CharacterP. karasbergenseP. parvifoliumP. lucensHabit (distal stems and lateral branchlets)Tapering, often spinescent, rigidCylindric, flexibleCylindric, rigidIndumentum on vegetative partsStrigulose (simple trichomes)Scattered sessile glandular trichomesDense short simple or sessile stellate trichomes (with 2 or 3 branches), usually with isolated dendritic trichomes in addition; glabrescentYoung growth (stems and leaves)Not glutinousCovered with a glutinous secretion (glossy)Not glutinousLeaf blade (shape)Oblanceolate to broadly oblanceolate or narrowly obovate, often subconduplicate towards apex; margins entireOblanceolate or narrowly obovate, flat or subreduplicate; margins entire, sometimes sparsely crenate-serrate towards apexOblanceolate to linear-lanceolate, broadly oblanceolate, broadly lanceolate, narrowly elliptic or ovate, flat; margins entireLeaf blade (size) (mm)Up to 19 × 74–30 × 2–11Up to 32 × 17Leaves (apex)Truncate, emarginate or acute; recurvedRounded to obtuse, apiculate; slightly recurvedAcute or obtuse; not recurvedBracteoles (shape; degree of fusion)Elliptic or narrowly ovate; free or free almost to baseLanceolate-ovate; clearly connate towards baseOvate to broadly ovate; connate towards baseBracteoles (colour)Cream-brownWhiteWhiteBracteoles (apex)Acute, attenuate or obtuseAcute, sometimes apiculateAcute with a long mucroBracteoles (indumentum abaxially)Strigulose; margins strigoseScattered sessile glands, towards base sometimes with very short glandular trichomes in addition; margins lanate with short-stalked glandular trichomes in additionPuberulent with short-stalked glandular trichomes in addition, some often robust, margins lanateBracteoles (size) (mm)10.5–11.5 × 5.0–6.210–12 × 4–518–20 × 15Corolla (size)ca. 20 mm long, 21 mm diam.ca. 13 mm long, 17 mm diam.ca. 24 mm long, 20 mm diam.Corolla (upper lobes) (shape; fusion)Obovate; freeOblong; connate for 25% of lengthObovate; freeCorolla (palate)ca. 10-ribbed5- or 6-ribbed5–7-ribbedCorolla (indumentum: outside)Glabrous except for few short- stalked glandular trichomesPuberulousScattered short-stalked glandular and isolated eglandular multi-cellular trichomesCorolla (colour of lobes)White or cream-white, occasionally with a faint lilac tingeMauve, white or white with lilac tingeMauveCorolla (nectar guides)Front lobe: pale yellow with purple patches Lateral lobes: purple Upper lobes: absentFront lobe: yellow with brown patches Lateral lobes: brown Upper lobes: brownFront lobe: cream Lateral lobes: beige Upper lobes: beigeFilaments (length) (mm)Short filaments: ca. 6.2 Long filaments: ca. 8.8Short filaments: ca. 4.3 Long filaments: ca. 5.7Short filaments: ca. 6.5 Long filaments: ca. 8.7Anthers (length) (mm)ca. 2.5ca. 2.2ca. 3.3Anthers (indumentum)Few simple trichomesScattered short-stalked glandular and few simple trichomesScattered short-stalked glandular trichomesStyle (indumentum)Puberulous towards basePuberulous with short-stalked glandular trichomes in additionPuberulousDistributionNamibia (Groot Karasberge in the ||Kharas Region)Botswana (Kgalagadi District), Namibia (Omaheke and Khomas Regions)Namibia (||Kharas Region) and South Africa (Northern Cape Province)
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