Podostemaceae
 
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Key A: Key to the Podostemaceae genera of Africa and Madagascar

(taken over from Cook & Rutishauser, Chapter on Podostemaceae in Kubitzki (ed.) Families & Genera of Vascular Plants, in press 2004; key modified by R. Rutishauser)

 
1. Tepals 3, imbricate and surrounding the flower buds, ovate to oblong-obovate; flower buds not enclosed in a spathella; capsules opening by 3 valves (widespread in Africa and Madagascar)
--> Subfamily Tristichoideae Tristicha (1sp.)
 
- Tepals 2 or occasionally 3 or 4, not imbricate and restricted to one side of the flower, linear to subulate; flower buds totally enclosed in a spathella; capsules opening by 2 valves
--> Subfamily Podostemoideae 2
 

2 . Stigma 1, semi-globose; stamens 3 or rarely 4, united only at the base (Angola)

-->Subfamily Podostemoideae Angolaea (1sp.)
 
- Stigmas 2, linear, horn-like or flattened and lobed; stamens 1, 2 or rarely 3, when 2 or 3 then born on an elongate andropodium
--> 3
 
3. Flowers erect or rarely oblique (slightly inclined) within the unruptured spathellas
Go on with subkey 13 or subkey 18
 
- Flowers inverted or strongly inclined within the unruptured spathellas
--> 4
 
4. Tepals 3, 1 each side of the andropodium and 1 born terminally on the andropodium between the stamens
--> 5
 
- Tepals 2, 1 each side of the andropodium and without an appendage between the stamens
--> 6
 
5. Capsules obovoid; capsule valves with 3 wide ribs, each extending from base to apex (Madagascar)
--> Thelethylax (2spp.)
 
- Capsules broadly ellipsoidal; capsule valves with 5 or 7 narrow ribs, those closest to the commissures not reaching the base and the apex (tropical W Africa)
--> Stonesia (4spp.)
 
6. Capsules smooth, globose or subglobose (tropical Africa)
--> Leiothylax (3spp.)
 
- Capsules with longitudinal ribs, globose to ellipsoid or cylindrical
--> 7
 
7. Ovaries and capsules flattened laterally; capsules with or without winged nerves
--> 8
 
- Ovaries and capsules circular in cross-section, not flattened; capsules without winged nerves
--> 9
 
8. Capsules strongly flattened, middle nerves winged and with apical horns; stamens 2 (Cameroons)
--> Winklerella (1sp.)
 
- Capsules slightly to strongly flattened, not winged; stamens 1 or 2 or 3 (tropical WAfrica) (6spp.)
--> Macropodiella
 
9. Capsules globose to subglobose
--> 10
- Capsules ovoid-ellipsoidal or partly cylindrical
--> 11
 
10. Stamen 1 or 2; pollen in dyads; capsules sessile or born on minute gynophores; pedicels less than 5 mm long (Madagascar, tropical East & S Africa)
--> Sphaerothylax (2spp.)
 
- Stamens 2 or rarely 3; pollen in monads; capsules born on up to 2 mm long gynophores; pedicels up to 15 mm long (Cameroons)
--> Zehnderia (1sp.)
 
11. Solitary flowers or flower clusters secund along the shoot; andropodium usually less than 1 mm long; stigmas conical, erect, rigid; capsules cylindrical to oblong (W Africa)
--> Dicraeanthus (2spp.)
 
- Flowers arranged around the shoot, rarely secund; andropodium occasionally much exceeding 1 mm long; stigmas linear, spreading or reflexed, flexible; capsules obovoid to ovoid or fusiform
--> 12
 

12. Capsule valves with 3 narrow (occasionally crest-like) ribs; capsules ovoid to ellipsoid or fusiform (species rich and widespread in tropical Africa)

--> Ledermanniella (46spp. in 2 nearly equal subgenera, see Keys D, E, F and G )
 

-Capsule valves with 3 wide and flattened ribs; capsules obovoid (Madagascar)
(Thelethylax minutiflora subsp. orientalis Perrier with only 2 tepals, i.e. additional third one lacking between the fused filaments (see Perrier 1952).

--> Thelethylax (2spp.)
 

13. Capsule valves slightly unequal; capsule sutures slightly acentric and oblique; usually one valve caducous, one valve persistent on pedicel or gynophor
(If you have difficulties with this character set, try subkey 18)

--> 14
 
- Capsule valves equal; capsule sutures centric; usually both valves persistent
--> 15
 
14. Stamen 1; capsules globose or subglobose; capsule valves with 3 wide ribs, each extending from base to apex (Cameroons)
--> Djinga (1sp.)
 
- Stamens 2, born on an andropodium; capsules asymmetrically ovoid and somewhat laterally flattened; capsule valves with 7 narrow ribs, those closest to the sutures not reaching the base and the apex (Madagascar)
--> Endocaulos (1sp.)
 
15. Capsules globose or subglobose, smooth and shiny (W Africa)
--> Letestuella (1sp.)
 
- Capsules ovoid to ellipsoid or fusiform, with ribs
--> 16
 

16. Flowering stems covered with many (at least 8), overlapping, scale-like leaves; stamens 2, born on an andropodium (Madagascar)

--> Paleodicraeia (1sp.)
 
- Flowering stems with elongate, simple or forked leaves or if leaves scale-like then rarely more than 4; stamen 1

--> 17

 
 

17 Leaves below the flowers scale-like, shorter than the flowers; capsules ovoid, laterally flattened; stigmas unequal, flattened, elliptic to ovate in outline (Nigeria)

--> Butumia (1sp.; now merged with Saxicolella )
 

- Leaves below the flowers linear or divided into linear segments, longer than the flowers; capsules elliptic to fusiform, terete; stigmas equal, linear (tropical W Africa)

--> Saxicolella (6spp.)
 
18 . Ovary and capsule globose or subglobose; capsules smooth or with 3 wide ribs per valve, each rib extending from base to apex; flowers slightly inclined (oblique) in spathella (W Africa)
--> 19
 
- Ovary and capsule ellipsoid to fusiform (or subglobose and somewhat laterally flattened; capsules with 3 - 7 ribs per valve; flowers usually erect in spathella [check] (Madagascar and W Africa)
--> 20
 
19. Capsules smooth and shiny; stamens 2 or 1 (Western to Southern Africa, incl. Cameroon)
--> Letestuella (1sp.)
 
- Capsule valves with 3 wide ribs, each extending from base to apex; stamen 1 (Cameroon)
--> Djinga (1sp.)
 
20. Stamens 2, born on andropodium; capsule with 5 or 7 ribs per valve, those closest to the sutures not reaching the base and the apex (Same pattern found in Stonesia (W Africa)! This feature needs to be checked again for Paleodicrea (see Cusset 1972: Fig. 2-4) ; stems short (or lacking), covered by 2 rows of overlapping, boat-shaped scales (Most of these scales are widened boat-shaped sheaths which have already dropped an apical thread-like blade!); elongate leaves (if present) usually thread-like and entire (Madagascar)
--> 21
 
- Stamen 1; capsule with 3 ribs per valve, each rib extending from base to apex ribs; stems with elongate, simple or forked leaves or if leaves scale-like then rarely more than 4 per
--> 22
 
21. Capsule valves with 7 narrow ribs; capsules asymmetrically ovoid and somewhat laterally flattened; flowers solitary at end of short stems which are covered with 7 or less overlapping scales
--> Endocaulos (1sp.)
 
- Capsule valves with 5 narrow ribs; capsule subglobose; flowering stems covered with many (at least 8) overlapping scales
--> Paleodicraeia (1sp.)
 
22. Leaves below the flowers scale-like, shorter than the flowers; capsules ovoid, laterally flattened; stigmas unequal, flattened, elliptic to ovate in outline (Nigeria)
--> bis. Butumia (1sp.; now merged with Saxicolella)
 

- Leaves below the flowers linear or forked into linear segments, longer than the flowers; capsules elliptic to fusiform, terete; stigmas equal, linear (tropical W Africa)

--> Saxicolella (6spp.)
 

 

 
       
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