Monographs Details: Diodia apiculata (Willd. ex Roem. & Schult.) K.Schum.
Authority: Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.

Spermacoce apiculata Willd. ex R. & S., Syst. Veg. 3: 531. 1818.

Spermacoce rigida Willd. ex R. & S., Syst. Veg. 3: 531. 1818, not Salisb. Prodr. 1796.

Spermacoce rigida H.B.K., Nov. Gen. & Sp. 3: 342. 1819, not Salisb. Prodr. 60. 1796.

Diodia rigida (Willd. ex R. & S.) C. & S., Linnaea 3: 341. 1828.

Diodia setigera DC., Prodr. 4: 563. 1830.

Diodia conferta DC., Prodr. 4: 563. 1830.

Diodia pulchella Brandegee, Univ. Calif. Publ. Bot. 10: 418. 1924.

Diodia rigida var barbicocca Schum., Mart. Fl. Bras. 6(6): 22. 1888.

Diodia rigida var marcantha Schum., Mart. Fl. Bras. 6(6): 22. 1888.

Diodia rigida var buchii Urb., Symb. Ant. 8: 687. 1921.

Salisbury (Prodr. 60. 1796) cited the name Spermacoce rigida for S. hispida, the name employed by Linnaeus in his Species Plantarum ed. 2. 147. 1762. This citation by Salisbury thus invalidates the use of Spermacoce rigida H.B.K. and Spermacoce rigida Willd. ex R. & S., published respectively in 1819 and 1818, these names being later homonyms. The first available name applicable to this taxon is Spermacoce apiculata Willd. ex R. & S. (Syst. Veg. 3: 531. 1818).

This taxon is highly variable and presents difficulties in delimiting the numerous entities involved. Any number of combinations could be made on the basis of differences in length of cauline hairs, pubescence or glabrity of fruits, the relative width and shape of the leaf blades, and the degree of pubescence of the stems. Schumann (Mart. FI. Bras. 6(6): 22. 1888) and Urban (Symb. Ant. 8: 667. 1921) have indicated varieties of this taxon, and other authors (de Candolle and Brandegee) have described species, all of which prove to be conspecific with Spermacoce apiculata. However, a precise evaluation of the limits of variations must await a future study of the type specimens involved. Until that time, it seems futile to draw up a key to separate the numerous variables encountered.

Of the obvious variations, two groups immediately come to our attention, 1) stems glabrous and 2) stems pubescent. Of the group with glabrous stems, there are those with pubescent fruits and those with glabrous fruits. Of the latter type, one finds variations of leaf shapes from linear-lanceolate or lanceolate to ovate or ovate-lanceolate. Of the group having pubescent stems, there are two principal types, (1) in which the pubescence of the stems is more or less uniformly short puberulous or hirtellous, and (2) in which the pubescence of the stems consists of elongate hairs on the angles and/or on the sides, with or without shorter puberulence. Of the first type having more or less uniformly short pubescence, one encounters variations with glabrous fruits or with pubescent fruits, and, in the latter group, those with the leaves glabrous above and those with the leaves pubescent above. Of the second type having elongate hairs on the angles and/or sides of the stems, variations are found in which the fruits are glabrous, varying from fruits twice as long as broad to those about as long as broad or only slightly longer than broad, while the variations showing pubescent fruits range from narrowly lanceolate or linear leaves to those broadly lanceolate or ovate-lanceolate.

Spermacoce rigida, described from the area of Caracas, Venezuela, has the leaves glabrous above, pubescent below, fruits glabrous, and stems hirtellous or short-puberulous (without elongate villous or pilose hairs on the angles). Specimens most closely approaching the original description of Humboldt and Bonpland, so far as the leaf shape and glabrity above with “hirto-pilosiusculis” pubescence below, are matched by Fendler 610 near Caracas, and Pittier 7185, above Caracas. However, other plants collected in the Caracas area differ from the type description of Spermacoce rigida H. & B. in having leaves glabrous on the lower surface (except for the hispidulous midrib), or in having fruits which vary in degrees of hispidulous pubescence at and near the apex (Pittier 11360 from Hacienda San Lazaro, near Caracas, varies in the pubescence of the fruits). Plants similar to the type described under Spermacoce rigida H. & B., but with the fruits varying in the amount of pubescence near the apex, are found scattered in the range of the taxon. The commonest variation in Venezuela is like the type described by Humboldt and Bonpland, i e with the leaves glabrous above, pubescent below, fruits glabrous, and stems short puberulous or hirtellous. This also appears to be the same type as is encountered in the type collection of Diodia setigera DC. Although the fruit of D. setigera is described by de Candolle as “glabro,” an examination of the Salzmann specimen shows a few hispidulous hairs at the apex of the fruit under high magnification.

Schumann (Mart. Fl. Bras. 6(6): 20. 1888) described the fruits of D. setigera as “superne subglabra,” and in his key (p 9-10) attempted to distinguish D. setigera from D. rigida (= D. apiculata) by supposed differences in leaf-base (in D. setigera “basi auriculata,” in D. rigida “basi truncata”), by leaf shape (in D. setigera “ovata,” in D. rigida “subulato-lanceolata”), by color of leaf drying (in D. setigera “sicc. flavido-viridia,” in D. rigida “sicc. cinerea”), and by the number of keels on the cocci (in D. setigera “capsula 5-carinata,” in D. rigida “capsula . . . tricarinata . . .”). However, these differences cannot be maintained, and Schumann’s key character of “capsula 5-carinata” for D. setigera is contradicted in his description of the species (p 20) in which the “coccis dorso tricarinatis” is stated, which is the same as in the description of the capsules of D. rigida. Moreover, Schumann reversed the characters of the leaf shape applicable to D. setigera and D. rigida. Actually, de Candolle described the leaves of D. setigera as “ovato-lanceolatis,” and this is confirmed by a photograph of the type specimen in the Delessert Herbarium and of an isotype specimen at K, as well as examination of the Salzmann collection at NY, which show the leaves as ovate to ovate-lanceolate. On the other hand, Humboldt and Bonpland describe the leaves of Spermacoce rigida as “lanceolatis,” and specimens range from narrowly lanceolate to ovate-lanceolate. Likewise, the specimen of Blanchet from Bahia, Brazil, at NY, referred to D. setigera, shows a few apical hispidulous hairs on the cocci, while a specimen collected by Wettstein & Schiffner from Sao Paulo near Taipas, shows glabrous fruit. The glabrity of the fruit does not serve to distinguish D. setigera from D. rigida, as the latter has glabrous cocci in the Caracas area, as well as pubescent-fruited plants from the type locality of Caracas. Moreover, the number of keels on the dorsal side of the cocci varies in the same specimen from 3 to 5, in some cases the 3 main keels are conspicuous as the only ones in evidence, in other cases two additional ones toward the margin are less evident; depending upon the prominence of the lateral keels near the margins, the cocci may be 3-or 5-keeled.

Other variations of this complex may show differences in corolla length and the amount of pubescence dorsally on the corolla lobes. In the West Indies most specimens show fruits sparsely pubescent near the apex combined generally with the character of either long or short hairs on the stems, as noted in South American material. In Central America and Mexico there are also variations having either glabrous fruits with either long pubescent stems or these completely glabrous, or pubescent-fruited types with either long or short pubescence on the stems. Likewise, in Mexico and Central America occur narrow-leaved extremes among the glabrous-stemmed and glabrous-fruited populations (Gentle 3688 and O’Neill 8695 from British Honduras). Diodia pulchella Brandegee from Chiapas, Mexico (Purpus 9221 from Hacienda Monserrate) is a variation with large corollas, the stems with a few elongate hairs on the angles and shorter hairs on the sides, the upper leaf surface glabrous, the lower surface glabrous or sparsely pubescent, the lower midrib hispidulous as are the margins, and the leaves broadly lanceolate and 3-4 mm broad. Diodia rigida var macrantha Schum. was described from plants of British Guiana and Para, Brazil, having glabrous or finely tomentellos stems and broad leaves with corollas 5-10(-14) mm long, but both narrow and broad-leaved types of plants with glabrous stems occur in the same area, and a photo of the type specimen shows one stem with narrower leaves, the other with broader leaves. Similarly, Urban’s treatment of var buchii includes both a variation with glabrous stems and one with long-pubescent stems. His var angustissima is an extremely narrow-leaved form with leaves only 0.5-0.8 mm wide and corollas 12 mm long, but is better considered another species, D. domingensis P. DC. (Urban, Symb. 8: 687. 1921).

Diodia rigida var barbicocca Schum. (Mart. Fl. Bras. 6(6): 22. 1888) refers to plants with long dense villous hairs at the apex of the cocci, leaves pubescent on both sides, and stems glabrescent or sparsely puberulous. This variation was described from Bahia, Rio de Janeiro, and Minas Gerais. Until a careful examination has been made of the specimens cited by Schumann, it is not possible to determine whether this variety includes only short-pubescent stemmed plants or those with elongate cauline hairs.

The following treatment indicates the combinations of variations and their occurrence geographically:

A. Variation with leaves glabrous above, short-pubescent to glabrous below, fruits glabrous, and stems with relatively short uniform pubescence.

VENEZUELA. Bolívar: Quebrada Supamo, Los Castillos, Bernardi 7952. Monagas: Chapopatal, cerca de Quiriquire, Lasser & Vareschi 4149. Carabobo: Valle de Vijirima cerca de Guacara, Pittier 8175. Miranda: Baruta, Trujillo & Fernandez 272. Aragua: Las Delicias, Agostini 609; Guamitas, Parque Nacional, Williams 10041. D.F.: La Quesera (Cotiza), arriba de Caracas, Pittier 7185; Cerros de Barrancas, Tamayo 1466; entre Cotiza y Los Venados, Allart 27; Caracas and Vicinity, L. H. & E. Z. Bailey 84; San Lazaro, around Caracas, Pittier 9752; around Caracas, Pittier 9606; near Caracas, Fendler 610. BRAZIL. Bahia: Salzmann (type of Diodia setigera); Blanchet s n.

B. Variation with leaves above, narrowly linear-lanceolate or linear, fruits shortly pubescent, and stems with relatively short uniform pubescence.

West Indies (St. Biminy, Antigua, Cuba, Hayti, Puerto Rico, Curacao, Dominican Republic), Central America, Mexico, and South America. VENEZUELA. Bolívar: Hato El Pilar, El Palmar, Trujillo 2246; carretera Villa Lola-Guasipati, Trujillo 2364; Altiplanicie de Nuria, east of Miamo, 5 km from Hato de Nuria, Steyermark 88364. Merida: between La Trampa and Lagunillas, Steyermark 56213. Falcon: Cerro Santa Ana, Paraguana, Tamayo 653. D.F.: Hacienda San Lazaro, cerca de Caracas, Pittier 11360. COLOMBIA. Huila: Cordillera Oriental, E of Neiva, Rusby & Pennell 1076; above Natagaima, Rusby & Pennell 1145; Quebrada de Angeles to Río Cabrera, Rusby & Pennell 353. BRAZIL. Gardner 1037.

C. Variation with leaves pubescent above, mainly ovate to ovate-lanceolate, fruits pubescent, and stems with relatively short uniform pubescence. This probably includes some specimens described under var barbicocca Schum. and D. conferta DC.

West Indies (Santo Domingo, Puerto Rico, Cuba); South America. VENEZUELA. Bolívar: Gran Sabana, between Kun and Uaduara-parú, valley of Río Kukenan, south of Mount Roraima, Steyermark 59057. BRAZIL. Distrito Federal, Restinga de Itapeba (Recreio dos Bandeirantes), Segadas-Vianna 3646.

D. Variation with leaves glabrous to long-pilose above, linear-lanceolate to broadly lanceolate, fruits short-pubescent, and stems long-pilose. This includes var Buchii Urb. in part, as to the branches with long-pilose hairs and broad leaves.

West Indies (Hayti, Santo Domingo, Puerto Rico, Cuba); Mexico, Central America; South America. VENEZUELA. Merida: Pueblo Nuevo, Jahn 687; Meseta near Tovar, Pittier 12776. Aragua: Maracay, Standin 93. Cojedes: Culebra Lagoon near San Carlos, Pittier 11696; “Limon,” San Carlos, Rudd 408. COLOMBIA. Santander: Mesa de los Santos, Killip & Smith 15231; Cordillera Oriental, Fosberg 22050. BRASIL: Minas Gerais: Serra do Itabirito, Planalto do Brasil, Serra do Espinhago, ca 45 km SE of Belo Horizonte, Irwin, Maxwell & Wasshausen 19892; Barbacena, Trinta 623, Fromm 1699; Turvo, Hoehne & Gehrt 17543. Santa Catarina: Laguna, Reitz & Klein 233.

E. Variation with leaves glabrous or glabrate above, scabridulous below, broadly ovate-lanceolate (5-7 mm broad), fruits pubescent, and stems long-pilose.

South America. VENEZUELA. Barinas: alrededores de Barinas, Aristeguieta & Montoya 2134. BRAZIL: Amapa: road to Amapa, Km 45, Pires & Cavalcante 52024.

F. Variation with leaves glabrous both sides or long-pilose above, mainly linear-lanceolate to lanceolate, 1.3-3 cm × 2-3 mm, fruits glabrous, about as broad as long or only slightly longer than broad, stems long-pilose on angles only or also short-pubescent on sides. Includes some specimens referred to D. setigera.

Mexico, Central America, South America. COLOMBIA. Guataqui, André K 1125. BRAZIL. Bahia: Blanchet s n. São Paulo: Jaragua bei Jaipas, Wettstein & Schiffner s n.

G. Variation with leaves glabrous both sides, fruits glabrous, 4 mm long, elongated and about as long as broad, stems long-pilose mainly on angles, otherwise glabrous.

VENEZUELA. Monagas: Campo ganadero, Maturin, Pittier 14354.

H. Variation with leaves glabrous and linear or linear-lanceolate, fruits shortly pubescent, stems glabrous. Includes that part of var buchii which pertains to glabrous stem.

West Indies (Antigua, Hayti, Puerto Rico, Dominican Republic, Cuba).

I. Variation with leaves glabrous, linear or linear-lanceolate, fruits glabrous, stems glabrous. Includes some specimens referred to var macrantha.

Central America, South America. BRITISH GUIANA. Berbice River, Wazanaman Ranch, Harrison & Persaud 1075; Berbice-Rupununi Cattle Trail, Berbice or Demerara County, Abraham 87. VENEZUELA. Terr. Delta Amacuro: sabanas en los Castillos de Guayana y Piacoa, Ramia 2204. Monagas: Hato de los hermanos Palacios, cerca de 8 km al sur de Maturin cerca de la carretera Maturin-Barrancas, Badillo 3708.

J. Variation with leaves glabrous, ovate-lanceolate or oblong-lanceolate, 1.5-2 cm × 4-7 mm, fruits glabrous, and stems glabrous. The corolla is campanulate and 6.58 mm long, glabrous without and within. This variant differs from var macrantha in its smaller campanulate corollas 6.5-8 mm long, with corolla lobes only 4-5 mm long, and the glabrous condition of the corolla without and within.

VENEZUELA. Anzoategui: llanos de Chive, El Guacimo, Pittier 15051; sabana de El Tigre, Vareschi 6398a; sabanas alrededores de Santomé, Pittier 14430. Terr. Delta Amacuro: entre los Castillos de Guayana y Piacoa, Ramia 2144.