Key F: First Key to the 20 species of Ledermanniella subgenus Phyllosoma
(according to Taylor 1954; Cusset 1983, 1987, 1997; Cook 2004; combined and modified by R. Rutishauser).
This is a modified and version of Cusset's (1983) key.
If you are not successful with this key, try also Key G and Key C !
1. Stems and all twigs densely covered with scales (see footnote 1); stems up to 15 cm long (often much less); roots often ribbon-like (if known at all; foliose roots in L. gabonensis ) 2
-- Scales do not cover stem completely; proximal stem portions with few or no scales at all; densely overlapping scales only found along the distal flower-producing twigs; main stems usually more than 15 cm long ( in some species much longer, up to 80 cm; only 1 - 2 cm in e.g. L. thollonii ); roots ribbon-like or foliose 10
2. Scales entire or with denticulate margin 3
-- Scales clearly dentate or digitate 5
3. Stems 4 - 6 cm long, simple or forked once; scales subulate to linear, 1 - 1.5 mm long; ribbons (0.5 mm wide); stamens 2; monads or dyads (?) L. mortonii C. Cusset [Sierra Leone]
-- Stems 2 - 3 cm long, branched; scales lanceolate to orbicular 4
4. Scales lanceolate to obovate; stamens 1 (or rarely 2); pollen in monads; roots foliose L. gabonensis C. Cusset [Congo; Gabon]
-- Scales orbicular (circular and flat) or nearly so; stamens 2; pollen in dyads; roots (?) L. boumiensis C. Cusset [Cameroon: Ntem; Gabon]
5. Scales digitate with 5 - 7 obtuse lobes, at least those in the upper portion of the main stems and the branches; stems up to 5 cm long; stamen 1, clearly shorter than ovary; pollen in monads; roots (?) L. digitata (Hess) C. Cusset [Angola]
-- Scales dentate; stamens usually 2 (rarely 3) [stamen also 1 in L. ledermannii and L. taylorii ] 6
6. Scales along branches with 5 - 7 (-10) triangular teeth; stems 2 - 15 cm long; stamens 2, as long or longer than ovary; pollen in monads; roots ribbon-like (up to 1 mm wide) L. cristata (Engler) C. Cusset [Angola; Cameroon: Malaka, Mari, Mvigli; Central African Republic; Gabon]
-- Scales tridentate (with additional conspicuous dorsal tooth in L. harrisii ; less conspicuous dorsal teeth occasionally or rarely observable in L. congolana, L. ledermannii and ... L. tenax ) 7
7. Capsule apex indented due to the median ribs having a short apical tooth each; stamens 2, shorter or only as short as ovary; pollen in monads; roots ribbon-like (up to 1mm wide) L. congolana (Hauman) C. Cusset [Zaïre]
-- Capsule devoid of apical teeth 8
8. Scales carrying a conspicuous dorsal tooth which is recurrent; plants look "prickly"; shoots 1 - 3 cm long, branched; stamen 2 (or 3); pollen in monads; c apsule with 8 ribs, only 6 of them conspicuous; roots (?) L. harrisii C. Cusset [Sierra Leone]
-- Scales usually without dorsal teeth; stamens 1 or 2; pollen in dyads; stems up to 5 cm long; roots ribbon-like 9
9. Capsule with 8 fine ribs, all equal; stamens (1 or) 2; stems 2 - 5 cm long, often branched; roots ribbon-like (2 - 3 mm wide) L. ledermannii (Engler) C. Cusset [Angola; Cameroon: Lobé, Mboro, Ndian; Gabon; Zaïre; Ivory Coast]
-- Capsule with 8 ribs, only 6 of them conspicuous (the two suture ribs inconspicuous); stamen 1; shoots less than 1 cm long, rarely branched; roots ribbon-like (c. 1mm wide) L. taylorii C.Cusset [Guinea] (see footnote 2)
10. Main stems elongate and unbranched, except for several reproductive short-shoots; roots ribbon-like (as far as known) 11
-- Stems branched; roots ribbon-like or foliose 12
11. Scales broad elliptical, margin nearly smooth to denticulate (rarely lanceolate with 5 prominent teeth); roots unknown; shoots 5 - 25 cm long; flowers or flower clusters opposite to forked foliage leaves; stamens 2 or 3, with free filaments slightly to clearly shorter than common stalk (andropodium) L. annithomae C. Cusset [Cameroon: Ntem; Gabon]
-- Scales lanceolate, digitate with 3 linear lobes as long as common sheath; roots ribbon-like (up to 1 mm wide); shoots 10 - 20 cm long; stamens 2, with free filaments much longer than common stalk (andropodium) L. paulsitae C. Cusset [Congo; Gabon]
12. Scales dentate with 5 - 7 marginal teeth, densily imbricate along flowering twigs; roots ribbon-like (up to 1 mm wide); shoots up to 50 or more cm long; stamens 2 (rarely 1 in L. fluitans ); pollen in monads 13
-- Scales entire or tridentate (additional dorsal teeth in L. tenax ); roots foliose or unknown (ribbon-like in L. tenax ); shoots up to 20 cm long ; stamens 1 or 2 14
13. Ovary apex with 6 short teeth, i.e. each of the 3 ribs per valve with an apical tooth L. warmingiana (Gilg) C. Cusset [Angola; Namibia]
-- Ovary with 8 ribs but without apical teeth L. fluitans (Hess) C. Cusset [Angola]
14. Flowers several towards the shoot tips; scales obovate, with 3 conspicuous distal teeth and (quite often) 1 or 2 inconspicuous dorsal teeth; robust plants with shoots up to 20 cm long; roots ribbon-like; stamens 2 L. tenax (C.H. Wright) C. Cusset [Angola; Zambia; Zimbabwe; Botswana]
-- Flowers solitary at the shoot tips or in the angles of forked twigs; scales not as above (never with additional dorsal teeth) 15
15. Scales restricted to the shoot tips; more proximal stem regions devoid of scales (few inconspicuous scales lower down in e.g. L. abbayesii ) 16
-- Scales present along the whole stems but often scantily lower down; roots foliose 18
16. Uppermost scales at shoot tips tridentate to trilobate, with median tooth longer than the lateral ones, or scales entire and subulate to narrow triangular; stems up to 30 cm long; stamens 1 or 2; pollen in dyads L. abbayesii (G. Taylor) C. Cusset [Guinea]
-- All scales entire ovate to cuneate or tridentate to trilobate; main leaves few, forked (if present at all); plants from Cameroon; roots (?); pollen in monads or dyads (?) 17
17. Main leaves without stipules; scales with broad base; scales (c. 0.6 x 0.2 mm), entire and ovate, or tridentate with nearly equal teeth; flowers arising along distal short-shoots which are densely covered with scales; stamens 2 L. bosii C. Cusset [Cameroon: Lobé Falls, Ntem Falls]
--Main leaves stipulate (?) ; scales cuneate, i.e. with narrow (petiole like) base, margin entire or denticulate; solitary flowers arising from the angles (axils) of uppermost stem forks; stamen number? L. kamerunensis (Engler) C. Cusset [Cameroon: Campo River] (see footnote 3)
18 . Most scales trilobate, often very slender, up to 5 mm long (median lobe often much longer than lateral ones); flowers and leaves arising from stem forks; foliage leaves forked (or trifurcate) several times into thread-like ultimate segments; shoots 4 - 10 cm long; stamens 2, with free filaments much shorter than common stalk (andropodium); pollen in monads; ovary sessile; roots foliose L. torrei C. Cusset [Mozambique]
-- Scales entire or with inconspicuous lobes; main leaves forked once or twice into linear segments; stems 1 - 15 cm long; ovary stalked (i.e. with gynophore); stamens 2 (or rarely 1), with free filaments as long or slightly shorter than common stalk (andropodium); ovary with short stalk (gynophore, c. 1mm or less) 19
19. Stems 1-2 cm long, unbranched or forked once; scales entire, triangular to ovate; capsule with 8 inconspicuous ribs; stamens 2; pollen in monads; roots foliose, deeply incised L. thollonii (Baillon) C. Cusset [Gabon]
-- Stems up to 15 cm long forked several times, with terminal foliage leaf in stem fork; scales lanceolate, entire or dentate or with 2 - 3 lobes; capsule with 6 prominent ribs (i.e. the 2 sutures not differentiated into ribs); stamens 2 (rarely 1); pollen in dyads; root (?) L. adamesii (G. Taylor) C. Cusset [Guinea, Sierra Leone]
Footnotes
1 This character may be misleading for certain species; e.g. elongate shoots of L. ledermannii (as far as I know) may have only few scales along proximal stem portions!
2 Check if L. taylorii is nothing but a dwarf form of the more widespread L. ledermannii !
3 This seems to be a badly known species (type in Berlin destroyed, according to Cusset 1983)
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