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Published In: Botanical Magazine 16: , t. 581. 1802. (Bot. Mag.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 6/6/2016)
Acceptance : Accepted
Taxon Profile     (Last Modified On 2/6/2017)
Description: Deciduous geophytes, with pale membranous cataphylls. Corm globose to obconic, axial in origin, tunics of finely to coarsely netted fibres. Stem mostly well developed, sometimes contracted, ± subterranean in 1 species. Leaves several, mostly basal, forming a 2-ranked fan, blade usually plane, linear to falcate with a definite main vein, rarely round to elliptic in section, occasionally margins undulate to crisped, inrolled, or winged, blades thus H-shaped in section, cauline leaves few and reduced; margin usually without vascular bundle and epidermal cells columnar and thickened, rarely with marginal bundle and epidermal cells unspecialized. Inflorescence a spike, rarely flowers solitary and terminal on axes, often secund; bracts relatively small, green and firm, or membranous to dry, outer usually 3-toothed, inner smaller than outer and 2-toothed or notched apically. Flowers usually zygomorphic, rarely radially symmetric, long-lived, bilabiate to salver-shaped or rotate, often orange to yellow, or red, pink, cream or white, often with darker veins, lower tepals often bearing bright yellow median tooth (callus) or raised ridge, occasionally sweetly scented, with nectar from septal nectaries; perianth tube funnel-shaped or cylindric, short or long; tepals subequal or unequal with dorsal largest and lower 3 forming a lip. Stamens unilateral, arcuate or diverging, rarely symmetrically disposed and erect; filaments included or exserted. Ovary globose; style filiform, unilateral or central, 3-branched distally, branches slender, curved, rarely shorter and expanded apically. Capsules cartilaginous, globose to ellipsoid. Seeds globose, flattened at chalazal end, smooth or rarely rugose, shiny, surface cells obscured by thick cuticle, ovular vascular trace excluded. Pollen monosulcate-operculate, operculum 2-banded, exine perforate-scabrate. Basic chromosome number x = 11.
Etymology: from the Latin, triton, a weathervane, for the variable orientation of the stamens in some species.
Revisionary account:
General Notes: Species 30, mainly southern Africa, also tropical Africa, centred in the winter-rainfall zone, with just 2 species occurring north of South Africa: Tritonia moggii Oberm. so far known from southern Mozambique is included in this account; T. laxifolia has an unusual disjunct distribution in southeastern South Africa and Malawi, Tanzania and Zimbabwe.

Originally limited to a small group of species with relatively large, short-tubed flowers with radially symmetric perianth, Tritonia now also includes species with short- to long-tubed, zygomorphic flowers. It forms part of a small clade of genera including Dierama, Duthiastrum, Ixia and Sparaxis defined by netted corm tunics, mostly radially symmetric flowers, more or less dry and papery or membranous bracts, and specialized, subglobose seeds with a smooth, glossy testa and a raphal vascular bundle excluded from the seed body during ripening. Tritonia is immediately related to Dierama and Ixia, the latter also often with 3-toothed bracts. Tritonia is separated from these two genera by its more sturdy and firm (not wiry) stem, leaves usually with specialized margins lacking a vascular bundle and having instead columnar epidermal cells with thickened walls, and possibly ancestrally zygomorphic flowers, often with the main vein on some or all lower tepals thickened or raised in a fleshy or bony callus or tooth. Similar teeth are developed elsewhere only in some species of Lapeirousia and Afrosolen (tribe Watsonieae). In several species the perianth is thin-textured with prominent, dark veins. Most species have a basic chromosome number of x = 11 (exceptionally x = 10).

Four species are anomalous in the genus in their leaf anatomy, possessing a marginal vascular trace with associated sclerenchyma cap and lacking the specialized, thickened epidermal cells that are characteristic of the other species of Tritonia (see De Vos, 1982b). These are the two Richtersveld endemics, T. delpierrei and T. marlothii, with narrow, leathery or subsucculent leaves, and two that have narrow, essentially centric leaves, T. bakeri, with stiffly linear, compressed elliptical or subterete leaves; and T. kamisbergensis with wiry, terete and fibrotic leaves.

 

Relationships among the species have not been tested using molecular sequences. We assume that the genus is ancestrally zygomorphic by analogy with other genera of Crocoideae containing species with both actinomorphic and zygomorphic flowers. In light of its close relationship with Dierama and Ixia, both of which have ancestrally radially symmetrical flowers, this assumption remains to be confirmed.

 

De Vos (1982, 1983) initially grouped the species into five sections, referring the majority to sect. Montbretia, defined by zygomorphic flowers with one or all of the lower tepals bearing a well-developed, tooth- or axe-like crest or callus on the midline near the base. Previously segregated at generic rank, this section is widely distributed from southern to south tropical Africa, and comprises three distinct groups of species identified by De Vos as possible subsections. The largest included nine species with orange to yellow or pink to red, strongly bilabiate flowers with large, axe-like calluses on the lower tepals. A second group included two species from the Richtersveld with subsucculent leaves without thickened marginal epidermis and pale, salver-shaped flowers, T. delpierrei and T. marlothii. The remaining two species, T. florentiae and T. karooica from the western central karroid zones of South Africa, were considered taxonomically distantly related by De Vos but both share similar long, crest-like calluses on the lower tepals and unusually large capsules.

 

Sect. Tritonia included four species with short-tubed, bowl-shaped, orange or pink flowers with a radially symmetrical perianth lacking well-developed calluses on the lower tepals, and with central or loosely unilateral stamens. One of the species included here, T. dubia, is almost certainly misplaced, differing from the other species in its ± rotate flowers with erect, symmetrically disposed stamens inserted near the top of the perianth tube, and larger, ellipsoid capsules. Similar capsules are found in T. laxifolia and T. moggii (sect. Montbretia), suggesting an alliance with those species. All members of sect. Tritonia are local endemics of southwestern South Africa.

 

The remaining species in the genus have zygomorphic flowers, usually without tepal calluses. The monotypic sect. Teretifoliae included just Tritonia kamisbergensis from Namaqualand, distinguished by its fibrous, subterete leaves, small, subherbaceous bracts, and red flowers. Sect. Pectinatae included four species with a dense, almost horizontal spike of pale pink to cream or white flowers with an elongate perianth tube. Three are fynbos endemics with uniquely modified leaves that develop longitudinal, flange-like outgrowths from the adaxial surface and margins. The fourth, T. tugwelliae from the western Great Karoo, has conventional plane leaves and small, uniformly pale bracts without dark upper margins and is thus evidently misplaced here. The residue of the species are accommodated in sect. Subcallosae, which was poorly and essentially negatively diagnosed as lacking the distinctive features of the other sections. The distinction between sect. Subcallosae and sect. Montbretia is, however, blurred by T. pallida, which sometimes has large, axe-like calluses on the lower tepals, and the two sections were combined by De Vos (1999). The species in sect. Subcallosae fall into two distinct groups based on flower shape: one with pale, long-tubed flowers restricted to the winter-rainfall region of South Africa, and a second with yellow or orange to red, funnel-shaped flowers, mainly from the eastern seaboard and near-interior. The long-tubed T. bakeri is anomalous in the section in its centric, terete or compressed leaves without true margins and its association with the other long-tubed species in the group may be mistaken.

 

Morphological evidence suggests that at least some of the species are currently misplaced in the existing sections but additional phylogenetic data are required to resolve relationships in the genus. Provisionally, we have rearranged some of the existing sections by removing anomalous taxa and have split others into smaller, morphologically homogeneous species groups. This arrangement serves to isolate the species clusters that we have been able to identify.
Pollination: Pollination in the genus has been little studied but the diversity of flower types in Tritonia signals a corresponding range of pollination systems. The ancestral system, as found in the species with colourful, funnel-shaped flowers, appears to be pollination by long-tongued anthophorid bees, which visit flowers to forage for nectar. This system occurs almost throughout the range of the genus but is overshadowed by two derived pollination systems in the southern African winter-rainfall zone. Here, species with pale, long-tubed flowers are adapted for pollination by long-proboscid horseflies (Tabanidae) and tangle-winged flies (Nemestrinidae), and species with a short-tubed, radially symmetric perianth, mostly with transparent patches or large dark markings, are adapted for pollination by hopliine scarab beetles.
References:

 

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1 Perianth actinomorphic, ± rotate with spreading tepals longer than tube; stamens either erect and central or weakly unilateral and diverging (2)
+ Perianth more or less zygomorphic, usually with posterior tepal larger, rarely subactinomorpic but then tepals much shorter than tube; stamens arcuate and unilateral with anthers ± contiguous (5)
2 (1) Flowering spike erect; flowers perfectly actinomorphic with stamens erect and inserted near top of tube; perianth tube only slightly shorter than tepals; capsules elliptic, longer than bracts Tritonia dubia
+ Flowering spike inclined; flowers slightly zygomorphic with the stamens arcuate and slightly spreading, inserted in lower half of tube; perianth tube half as long as tepals or less; capsules subglobose, shorter than bracts [sect. Tritonia] (3)
3 (2) Tepal claws without wide hyaline margins; tepals unmarked or outer tepals with dark blotch at base of limb; perianth tube yellow with prominent star-shaped yellow patch outlined with red in throat Tritonia deusta
+ Tepal claws with wide hyaline margins; tepals unmarked; perianth tube with hardly any yellow colouring in throat (4)
4 (3) Perianth bright orange-red to vermilion Tritonia crocata
+ Perianth pale to bright mauve pink Tritonia squalida
5 (1) Spike strongly deflexed and almost horizontal, ± pectinate-secund, closely flowered; flowers long-tubed, white to pink with red streaks on lower tepals; leaves with margins crisped-undulate or inrolled or winged (6)
+ Spike suberect and not as above; leaves plane or subterete but margins not variously elaborated (9)
6 (5) Leaves distichous, falcate, margins crisped or undulate; bracts 3–8 mm long, pale without conspicuous dark upper margins; tepals 7–9 × 2–4 mm long [sect. Pseudopectinatae] Tritonia tugwelliae
+ Leaves not clearly distichous, more or less narrowed below and pseudopetiolate, margins inrolled and straight or undulate crisped; bracts 5–15 mm long, with conspicuous dark reddish brown, crisped upper margins; tepals 12–25 × 3–13 mm [VII. sect. Pectinatae] (7)
7 (6) Flowers almost salver-shaped, lower tepals with two short red lines near base; perianth tube straight, (17–)20–25 mm long; leaves often narrowed between base and sheath into slender petiolar portion, blade linear-lanceolate with margins in rolled; plants from Piketberg Tritonia lancea
+ Flowers bilabiate, lower tepals with lozenge-shaped red markings; perianth tube slightly curved, (20–)40–60(–85) mm long; leaves otherwise; plants not from Piketberg (8)
8 (7) Leaf blade weakly involute with crisped or undulate margins Tritonia undulata
+ Leaf blade X- or H-shaped with straight margins Tritonia cooperi
9 (5) Leaves wiry, centric and terete or compressed-cylindric in section, striate with several translucent veins, 1–3 mm diam. (10)
+ Leaves plane and linear to lanceolate or falcate, with evident midrib (11)
10 (9) Flowers obliquely funnel-shaped, ruby-red; stamens inserted in lower half of tube; bracts ± green and leathery with membranous margins; plants from Namaqualand [X. sect. Teretifoliae] Tritonia kamisbergensis
+ Flowers salver-shaped with long, slender tube; stamens inserted near mouth of tube; bracts papery or membranous throughout; plants from Little Karoo [sect. Subteretifoliae] Tritonia bakeri
11 (9) Flowers ± salver-shaped with sub-cylindric perianth tube widening slightly in upper 1/2 to ± 2 mm diam. at mouth; bracts green and leathery in lower half; lower tepals puberulous on upper surface; leaves slightly succulent with one or two veins evident but not raised; plants from Richtersveld and Bushmanland [sect. Deserticola] (12)
+ Flowers with funnel-shaped or cylindric perianth tube widening conspicuously above to ± 5–8 mm diam. at mouth; bracts membranous or papery throughout; lower tepals not puberulous on upper surface; leaves not sub-succulent, always with midrib evident and raised; plant not from Richtersveld (13)
12 (11) Flowers pale creamy yellow; perianth tube 12–22 mm long Tritonia delpierrei
+ Flowers pale mauve to purple; perianth tube 28–42 mm long Tritonia marlothii
13 (11) Stems contracted or plants acaulescent; leaves falcate, leathery; calluses long and crest-like, crisped or undulate and much longer than high [sect. Montbretiopsis] (14)
+ Stems well-developed; leaves suberect or spreading; calluses reduced to low ridges or axe-like but never crisped or undulate (15)
14 (13) Plants shortly caulescent; inflorescence a spike of one or more flowers; flowers pale or dull orange with dark veins; perianth tube sharply curved, about twice as long as tepals; plants flowering in spring, in August and September Tritonia karooica
+ acaulescent; inflorescence of one or more 1-flowered units; flowers bright yellow; perianth tube almost straight, about as long as tepals; plants flowering in winter in May and June Tritonia florentiae
15 (13) Flowers white to pink; perianth tube longer than tepals, narrow and cylindric, widening only near mouth; anthers apiculate; leaves never with prominent submarginal vein [sect. Pallidae] (16)
+ Flowers creamy yellow, orange or red; perianth tube shorter or longer than tepals, usually funnel-shaped and widening in upper half; leaves with or without prominent submarginal vein (18)
16 (15) Leaves linear, 1–3 mm wide, as long as flowering stem or longer; plants flowering in December Tritonia linearifolia
+ Leaves lanceolate, 4–15 mm wide, shorter than flowering stem; plants flowering September to November (17)
17 (16) Leaves stiffly erect, attenuate, mostly 4–10 mm wide; bracts attenuate-aristate, with outer mostly 15–40 mm long, much exceeding inner in lower part of spike; plants from southern coastal mountain ranges Tritonia flabellifolia
+ Leaves softer and suberect or spreading, acute to acuminate, mostly 10–15 mm wide; bracts ± 3-toothed, acute or acuminate, outer mostly 7–10(–15) mm long, always only slightly longer than inner; plants from Little Karroo and S slopes of the western Langeberg Tritonia pallida
18 (15) Calluses on lower tepals reduced to low, thickened median ridge or rarely triangular and about as high as long; leaves always with prominent submarginal vein (19)
+ Calluses on lower tepals axe-like, higher than long, rarely lacking but then leaves without prominent submarginal vein: [II. sect. Montbretia] (21)
19 (18) Leaves linear, 1.5–4 mm wide; flowers with prominent, triangular calluses on lower tepals Tritonia drakensbergensis
+ Leaves narrowly lanceolate, 5–20 mm wide; flowers without calluses on lower tepals (20)
20 (19) Flowers cream, straw or pale yellow, sometimes with apricot or pale orange tints toward tip of perianth or on reverse, usually with dark veining; flowering August to November (rarely December) Tritonia gladiolaris
+ Flowers red, orange-red or pink, rarely with dark veining; flowering (December) January to April Tritonia disticha
21 (18) Leaves linear, flaccid, mostly 1.5–2.0 mm wide; flowers without calluses on lower tepals; filaments short, 4–5 mm long, included in perianth tube; plants from Cederberg in Western Cape Tritonia cedarmontana
+ Leaves various, usually wider; flowers always with calluses on median or all lower tepals; filaments 6–18 mm long, shortly or well exserted from perianth tube; plants not from Cederberg (22)
22 (21) Perianth tube (18–)20–40 mm long and about twice as long as the dorsal tepal (23)
+ Perianth tube (6–)10–15(–20) mm long, about as long as the dorsal tepal or rarely up to one and a half times as long (24)
23 (22) Plants not stoloniferous; leaves without prominent submarginal vein; flowers pale to bright yellow, sometimes flushed with apricot; all 3 lower tepals with well-developed calluses; plants of Western and Eastern Cape Tritonia chrysantha
+ Plants stoloniferous; leaves with prominent submarginal vein; flowers orange-pink or salmon-pink; lower median tepal with well-developed callus; plants of southern Mozambique Tritonia moggii
24 (22) Leaves linear, (1–)2–6 mm wide, stiffly erect, closely several-veined and striate when dry; plants mostly 300–600 mm tall (25)
+ Leaves various but not as above, always with a prominent main and sometimes submarginal vein but other veins inconspicuous; plants mostly less than 300 mm tall; from southeastern South Africa (also subtropical Africa):Leaves various but not as above, always with a prominent main and sometimes submarginal vein but other veins inconspicuous; plants mostly less than 300 mm tall; from southeastern South Africa and subtropical Africa) (26)
25 (24) Flowers dark red drying blackish purple; leaves with main and submarginal veins prominent; plants from Eastern Cape near Butterworth Tritonia atrorubens
+ Flowers orange not drying darl; leaves with all veins equally prominent; plants from the northern provinces of South Africa and Botswana Tritonia nelsonii
26 (24) Plants flowering in late summer and autumn, (January) March to May; corms often with stolons bearing a small cormlet; capsules ellipsoid, (12–)15–22 mm long, erect and pressed against the rachis Tritonia laxifolia
+ Plants flowering in winter and spring, August to November (December); corms without stolons; capsules ovoid to ellipsoid, 6–10 mm long, not pressed against the rachis (27)
27 (26) Leaves with thickened submarginal vein more prominent than midrib Tritonia strictifolia
+ Leaves with submarginal vein unthickened or less prominent than main vein (28)
28 (27) Leaves ± spirally twisted and margins usually undulate or crisped; plants from Anysberg and Montagu to Barrydale in Western Cape Tritonia watermeyeri
+ Leaves not spirally twisted or crisped-undulate; plants from east of Barrydale in Western and Eastern Cape
29 Leaves linear, mostly, 1–2(–3) mm wide, sometimes as long as stem Tritonia parvula
+ Leaves lanceolate, (4–)6–10(–12) mm wide, ± 1/2 as long as stem Tritonia securigera
 

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