Acanthopsis, HARV. BASED ON A COMBINATION OF TRICHOME AND

Steyn, Hester M. & Van Wyk, Abraham E., 2021, Taxonomic significance of trichomes in the genus Acanthopsis Harv. (Acanthaceae, tribe Acantheae), Adansonia (3) 43 (14), pp. 163-176 : 172-173

SIMPLIFIED KEY (FOR FULL VARIATION SEE TABLES 3 AND 4) TO THE SPECIES OF ACANTHOPSIS HARV. BASED ON A COMBINATION OF TRICHOME AND MORPHOLOGICAL CHARACTERS.

Note: for distinction between semi-dense and dense inflorescences, see Steyn & Van Wyk (2017b).

1a. Leaves with dense indumentum of appressed, anvil-shaped (asymmetrically T-shaped) trichomes (Type A2) giving plants a glaucous appearance ............................................................................................ 2

1b. Leaves with indumentum of varied trichomes but not dense, appressed, anvil-shaped trichomes (Type A2); rarely glaucous ( A. erosa ), but then due to Type A1 trichomes ................................................... 8

2a[1]. Plants erect, virgate shrublets (> 25 cm tall) with well-developed branches and distinct internodes; leaves scattered (well-spaced) along woody stem .......................................................................................... 3

2b. Plants cushion-shaped subshrubs (usually <20 cm tall) with gnarled stems and reduced internodes; leaves tufted or in basal rosette .................................................................................................................... 5

3a[2]. Floral bracts with central primary spine distinctly spathulate .................... A. spathularis (Nees) Schinz

3b. Floral bracts with central primary spine not spathulate ..................................................................... 4

4a[3]. Leaf base attenuate; inflorescences clearly pedunculate; basal floral bracts with spines up to 15 mm long .................................................................... A. dregeana H.M.Steyn subsp. dregeana (also see A. erosa )

4b. Leaf base usually auriculate; inflorescences subsessile; basal floral bracts with spines 20-25(-30) mm long ............................................................................ A. dregeana H.M.Steyn subsp. longispina H.M.Steyn

5a[2]. Leaves with non-glandular, ornamented, multi-cellular trichomes (Type B) ...................................... 6

5b. Leaves without non-glandular, ornamented, multi-cellular trichomes (Type B) ................................. 7

6a[5]. Leaf base not decurrent with spines 5-8 mm long; inflorescences pedunculate, semi-dense, 8-10 mm in diameter ............................................................................................. Acanthopsis glauca (Nees) Schinz

6b. Leaf base decurrent with spines 4-6 mm long; inflorescences sessile, dense, 12-14 mm in diameter....... .................................................................................................................... A. ludoviciana H.M.Steyn

7a[5]. Leaves with spines on margins 2(-3) mm long; inflorescences dense ......... A. adamanticola H.M.Steyn

7b. Leaves with spines on margins 4-7(-8) mm long; inflorescences semi-dense ....... A. insueta H.M.Steyn

8a[1]. Leaves villose due to dominance of long, non-glandular, multi-cellular trichomes with nodes distinctly swollen (Type D) .............................................................................................................................. 9

8b. Leaves variously hairy, but not villose .............................................................................................. 10

9a[8]. Inflorescences semi-dense, 80-120(-150) mm long ................................... A. scullyi (S.Moore) Oberm.

9b. Inflorescences dense, 25-50(-70) mm long .......................................................... A. villosa H.M.Steyn

10a[8]. Plants erect, virgate shrublets (> 25 cm tall) with well-developed branches and distinct internodes; leaves scattered (well-spaced) along woody stem ........................................................................................ 11

10b. Plants cushion-shaped subshrubs (usually <20 cm tall) with gnarled stems and reduced internodes; leaves tufted or in basal rosette .................................................................................................................. 12

11a[10]. Leaves and bracts with indumentum almost exclusively composed of non-glandular, ornamented, erect or spreading unicellular trichomes (Type A1); inflorescences semi-dense ............... A. erosa H.M.Steyn

11b. Bracts with indumentum mainly composed of long, non-glandular, multicellular trichomes (Type D) and glandular, multicellular trichomes with short stalks (Type F); inflorescences dense... A. horrida (Nees) Nees

12a[10]. Floral bracts with glandular, multicellular trichomes with 3-celled stalk and viscid head (Type G) ...... 13

12b. Floral bracts without glandular, multicellular trichomes with 3-celled stalk and viscid head (Type G) .... 15

13a[12]. Trichomes glandular, multicellular with 3-celled stalk and viscid head (Type G) dominant on floral bracts, and present on leaves ......................................... A. hoffmannseggiana (Nees) C.B.Clarke (typical form)

13b. Trichomes glandular, multicellular with 3-celled stalk and viscid head (Type G) present (not dominant) on floral bracts, but absent on leaves ............................................................................................... 14

14a[13]. Leaf base not decurrent; inflorescences dense, 12-14 cm in diameter; floral bracts ending in 5 primary spines ......................................................................................................... A. pagodiformis H.M.Steyn

14b. Leaf base decurrent; inflorescences semi-dense, 14-16(-20) cm in diameter; floral bracts ending in 3 primary spines ............................................................................ A. tetragona H.M.Steyn subsp. tetragona

15a[12]. Leaves shiny, glabrous or almost so .................................................................................................. 16

15b. Leaves not shiny or glabrous; variously hairy ................................................................................... 17

16a[15]. Leaf base decurrent; floral bracts with non-glandular uni- and multicellular trichomes (Types C and D) frequent to common; inflorescences dense, (8-) 10-13 mm in diameter .................. A. tuba H.M.Steyn

16b. Leaf base not decurrent, floral bracts without non-glandular uni- and multicellular trichomes (Types C and D); inflorescences semi-dense, 12-16 mm in diameter ............................... A. nitida H.M.Steyn

17a[15]. Leaves and bracts with long, non-glandular, multi-cellular trichomes (Type D) ............................... 18

17b. Leaves and bracts without long, non-glandular, multi-cellular trichomes (Type D) ......................... 21

18a[17]. Spines on leaf base 3-5 mm long; floral bracts without short, non-glandular, unicellular trichomes (Type C) ..................................................................................................... A. carduifolia (L.f.) Schinz

18b. Spines on leaf base absent or 1-3 mm long; floral bracts with short, non-glandular, unicellular trichomes (Type C) frequent to common ........................................................................................................ 19

19a[18]. Leaves distinctly petiolate, margins dentate-spinose with spines 1-3 mm long; spines on leaf base absent; inflorescences dense, 13-15 mm in diameter ............................................................. A. disperma Nees

19b. Leaves sessile, margins coarsely dentate-spinose with spines 1-4(-7) mm long; spines on leaf base 1-3 mm long; inflorescences dense or semi-dense, 7-12 mm in diameter ...................................................... 20

20a[19]. Leaves with short, glandular, multicellular trichomes (Type F) rare to occasional; inflorescence semi-dense, 70-140 mm long, 7-9 mm in diameter ..................................................... A. glabra (Nees) H.M.Steyn

20b. Leaves with short, glandular, multicellular trichomes (Type F) frequent to common; inflorescence dense, 50-80 mm long, 9-12 mm in diameter .......... A. hoffmannseggiana (Nees) C.B.Clarke (Pofadder form)

21a[17]. Leaf base decurrent; inflorescences semi-dense with floral bracts ending in 3 primary spines ................ ........................................................................ A. tetragona H.M.Steyn subsp. pedunculata H.M.Steyn

21b. Leaf base not decurrent; inflorescences semi-dense or dense with floral bracts ending in 5 primary spines .............................................................................................................................................. 22

22a[21]. Leaves dentate-spinose, spines on margins 1-3 mm long, 1 mm long at base; inflorescences 10-12 mm in diameter; floral bracts with short, glandular, multicellular trichomes (Type F) rare to occasional ...... ................................................................................................................... A. dispermoides H.M.Steyn

22b. Leaves coarsely dentate-spinose, spines 3-6 mm on margins, 3-5 mm long at base; inflorescences 8-10 mm in diameter; floral bracts with short, glandular, multicellular trichomes (Type F) frequent to common ............................................................................................................. A. glandulopalmata H.M.Steyn