Podostemum rutifolium Warming ("Podostemon rutifolius"), Vidensk. Selsk. Skr., ser. 6, 9(2): 129. 1899.-TYPE: BRAZIL. Santa Catarina: Rio Itajahy, Fritz Muller s.n. (distributed as Schwacke 5053) (holotype: C!; isotypes: L! R!). Plant Description: Roots 0.2-3.4 mm wide. Stems monomorphic, arising 0.7-11 mm apart along root, 0.1-94 mm long. Leaves sessile or petiolate, upright, arising in a ca. 180° distichous arrangement, simple (occasional near stem base) to 1-5 times dichotomously to subdichotomously divided, simple leaves 0.7- 9.3 mm long, 0.2-2.7 mm wide, entire, apices rounded, blunt, acute or apiculate; compound leaves divided to the midrib or not, 1.2-21 mm long; divisions arising in a 2-dimensional manner; ultimate leaf divisions 0.3-9 mm long, 0.2-1.5 mm wide, flattened, apices rounded, blunt, acute or apiculate, with or without a faint central vein; petioles 0.1-5.3 mm long, rounded, elliptical or flattened in cross section; leaf bases symmetrical, attached perpendicular to stem axis; stipules composed of an extension of the boat-shaped leaf base; persistent or caducous, often hardened and darkened on older stems, 0.01-0.6 mm long, with 2 flattened triangular teeth, teeth 0.05-0.4 mm long. Flowers 1-5 per stem; spathella 1.3-4.5 mm long, 0.7- 2.1 mm wide, smooth to minutely papillate, apex rounded or with a nipple; tepals 3, linear or awl­-shaped, straight or curved, apex acute or blunt; lateral tepals 0.5-1.7 mm long; andropodial tepal 1-2, 0.1-1.2 mm long; andropodium 0.3-1.4 mm long prior to anthesis, during anthesis to 0.6-4.2 mm; stamens 2; filaments 0.2-1 mm long prior to anthesis, during anthesis to 0.2-2 mm; anthers 0.2-1.7 mm long, 0.4-1 mm wide; pollen dyads 22-35 µm long, 12-23 µm wide; ovary 0.4-2.1 mm long, 0.4-1.5 mm wide; stigmas entire, 0.2-1.1 mm long prior to anthesis, during anthesis to 0.3- 2.8 mm; pedicels 0.2-2.3 mm long prior to anthesis, during anthesis to 1.1-6.6 mm. Capsules 1.2-2.3 mm long, 0.8-1.6 mm wide; 6 ribbed (3 per valve), suture margins also rib-like; pedicels in fruit 1.2-7.8 mm long; seeds 0-85 per capsule, 0.2-0.6 mm long, 0.1-0.4 mm wide.

We recognize two subspecies of P. rutifolium, which we separate primarily by their geographical distribution rather than morphology. Subspecies rutifolium is found mostly in southern Brazil and Argentina, whereas subsp. ricciiforme occurs in Mexico, Belize, Costa Rica, and Colombia. The respective geographic ranges are separated by ca. 3,000 km. One subtle morphological character that seems to distinguish the two subspecies is the form of the lateral tepals: blunt and darkened in subsp. ricciiforme versus acute and not darkend in subsp. rutifolium; however, P. ricciiforme seldom flowers, and thus it is yet unclear how stable this character is.

The subspecies exhibit overlapping variation in most qualitative leaf, stem, flower, and fruit characteristics. Although the differences are not supported statistically, there is a tendency for plants of subsp. ricciiforme to be smaller than those of subsp. rutifolium. For example, leaves of subsp. ricciiforme range from 0.7-1.3 cm long, whereas those of subsp. rutifolium range from 0.1-2.1 cm long. Similar evidence of smaller size in subsp. ricciiforme pertains to petiole, stem, and stipule length.

Both subspecies have leaves that are simple or several times divided, but the incidence of simple leaves differs. Simple leaves are common in subsp. ricciiforme. In some populations they make up the majority of leaves on the stem. In contrast, plants of subsp. rutifolium typically have simple leaves only at the stem base.

The incidence of flowering and seed set differs between the two subspecies, although it is difficult to apply such characters in taxon recognition. Abundant flowering and seed production occurs in subsp. rutifolium, similar to other species in the genus. In contrast, plants of subsp. ricciiforme seldom flower. Flowers that are produced often have an abberant form (e.g., extra tepals or abnormal stamens). We have seen only few seeds in all the materials studied of subsp. ricciiforme. The reasons for the lack of flowering and seed set are unknown.

Warming (1899, p. 129) lists one collection in the protologue for P. rutifolium: "In Brasilia, Estado de Sta Catharina ad Blumenau, Rio d'ltajahy, leg. Fritz Muller (Herb. Schwacke 5053) et Dr. Guil. Muller, 1884." There is one specimen in C (upper envelope on sheet number 133/96 42) that corresponds to this information, but lacks a date. We con­sider this specimen to be the holotype. Royen (1954, pp. 241) lists the type as Schwacke 5053 in C, although he makes no reference to Fritz Muller. An isotype is located in L (10015/61), which likely represents a fragment removed from the type in C. Podostemum rutifolium subsp. rutifolium.

Podostemum ostenianum Warming ("Podostemon osteniana"), Vidensk. Selsk. Skr., ser. 6, 9(2): 127. 1899.-TYPE: URUGUAY. Salto: 15 Dec 1892, Osten 2903 (lec­totype, here designated: C!, pressed specimen; isolectotypes: B, C-spirit, jar no. 11454! L!).

  Plant Description: Roots 0.2-3.4 (1) mm wide. Stems arising 1.1-11 (4.4) mm apart along root, 0.1-94 (6) mm long. Leaves simple (occasional near stem base) to 1-5 (2) times dichotomously to subdichotomously divided, simple leaves 0.9-6.1 (2.8) mm long, 0.2-1.5  (0.7) mm  wide, entire, apices rounded, blunt, acute or apiculate; compound leaves divided to the midrib or not, 1.2-21 (5.7) mm long; ultimate leaf divisions 0.3-9 (1.8) mm long, 0.2-1.5 (0.5) mm wide, flattened, apices rounded, blunt, acute or apiculate, with or without a faint central vein; petioles 0.1-5.3 (1.1) mm long, elliptical or flattened in cross section; leaf bases symmetrical; stipules 0.01-0.4 (0.3) mm long, often hardened and darkened on older stems, with 2 flattened triangular teeth, teeth 0.05-0.4 (0.1) mm long. Flowers 1-5 (1) per stem; spathella 1.3-4.5 (2.6) mm long, 0.8-2.1  (1.2)  mm  wide,  tepals  3, apex acute; lateral  tepals  0.6-1.7 (1) mm long; andropodial tepal 0.2-1.2 (0.8) mm long; andropodium 0.3-1.4 mm (0.7) mm long prior to anthesis, during anthesis to 0.6-4.2 (2.4) mm; stamens 2; filaments 0.2-1 (0.5) mm long prior to anthesis, during anthesis 0.2-2 (0.9) mm; anthers 0.2-1.7 (1.1) mm long, 0.4-1 (0.8) mm wide; pollen dyads 27-35 (30) µm long, 17-23 (20) µm wide; ovary 0.4-2.1 (1.5) mm long, 0.4-1.5 (1.1) mm wide; stigmas 0.2--0.9 (0.5) mm long prior to anthesis, during anthesis to 0.3-2.8 (1) mm; pedicels 0.2-2.3 (0.6) mm long prior to anthesis, during anthesis to 1.1-6.6 (4.1) mm. Capsules 1.2-2.3 (1.8) mm long, 0.8-1.6 (1.4) mm wide; pedicels  in fruit  2-7.8  (4.3)  mm long; seeds 0-85 (5)  per capsule,  0.2--0.6  (0.3) mm long, 0.1--0.4 (0.2) mm wide. 

Distribution. Southeastern Paraguay, northeastern Argentina (Corrientes, Misiones), western Uruguay (Uruguay River), and southern Brazil (Parana, Rio de Janeiro, Santa Catarina, Rio Grande do Sul); typically locally abundant, dense growth on horizontal to vertical rock surfaces; sea level to 900 m. 

Podostemum rutifolium subsp. rutifolium can occur alone or with P. distichum, P. irgangii, P. muelleri, Tristicha trifaria, and at least one species of Apinagia. 

REPRESENTATIVE SPECIMENS. Argentina. CORRIENTES: Arroyo Chimiray, 10 km SE of Azara, Depto. Santo Tome, Tressens et al. 3850 (CTES, GH).-MISIONES: Arroyo Chimiray, Depto. Apostoles, Guaglianone et al. 907 (LP); Arroyo Uruguay, puente camino viejo, Depto. lguazu, Guaglianone et al. 997 (LP); Parque Na­cional Iguazu, lguazu, Schinini 16249 (CTES, LP); Arroyo Uruguay, Depto. Iguazu, Tur 1307 (LP); Arroyo Aguaray, Depto. Iguazu y El Dorado, Tur 1314 (LP); Parque Nacional Iguazu, Saito Dos Hermanas, lguazu, Tur & Guaglianone 2025 (LP); Parque Nacional Iguazu, S de Puerto Canoas, lguazu, Tur & Guaglianone 2029 (LP); Arroyo Chimiray, balneario de Azara, Depto. Apostoles, Tur et al. 2103 (LP, MEXU, WCSU); Saito del Arroyo Tabay, Depto. San Ignacio, Tur et al. 2107 (LP, MEXU, WCSU); Saito del arroyo Capiovo, Depto. Libertador General San Martin , Tur et al. 2113 (LP, MEXU, WCSU); Rio Cuna piru, Depto. Libertador General San Martin, Tur et al. 2115 (LP, MEXU, WCSU); Rio Puray Mini, Depto. El Dorado, Tur et al. 2117 (LP, MEXU, WCSU); Parque Nacional Iguazu, Saito Bossetti, Rio Iguazu, Depto. Iguazu, Tur et al. 2120, 2121, 2130-2132 (LP, MEXU, WCSU); Rio lguazu, Parque Nacional lguazu, above the falls ca. 2 km, Depto. lguazu, Tur et al. 2125, 2126 (LP, MEXU, WCSU); Parque Nacional Iguazu, Saito Dos Hermanas, Rio Iguazu, Tur et al. 2134 (LP, MEXU, WCSU); Parque Nacional lguazu, Rio Iguazu, ca. 3 km upstream of falls, El Nandu camping area, Tur et al. 2139 (LP, MEXU, WCSU); Arroyo Piray Guazu, Depto. San Pedro, Tur et al. 2142 (LP, MEXU, WCSU); Arroyo Paraiso or lpane, road to Mocona, 34 km from Soberbio, Depto. Guarani, Tur et al. 2146 (LP, MEXU, WCSU). Brazil. PARANA: [unclear locality], Lindeman & de Haas 3536 (U); Rio Parana, near Guaira, Lindeman & Haas 4438 (U); Parque Nacional do Iguacu, Rio lguacu, Vital & Buck 11992 (NY).-RIO GRANDE DO SUL: Lagoa dos Patos, Sao Lourenco, lrgang et al. s.n. (ICN); Arroyo Grande, Silveira Martins, Lindman A1233 (L, S); Rio de Vacacai, below a dam called Barragem Corsan, Philbrick et al. 5011 (ICN, MEXU, WCSU); a river that drains into Rio Camaque, 5 km SE of Piratini, Philbrick et al. 5013, 5014 (ICN, MEXU, WCSU); along BR-392, 1-2 km NW of Piratini, Philbrick et al. 5018 (ICN, MEXU, WCSU); Lagoa dos Palos, Sao Lourenco do Sul, Philbrick et al. 5021 (ICN, MEXU, WCSU); arroyo do Lajeado, ca. 20 km NE of Santo do Erval, Philbrick et al. 5025, 5026 (ICN, MEXU, WCSU); 45 km SE of Dom Pedrito, Philbrick et al. 5031 (ICN, MEXU, WCSU); small river that drains into Rio Jaguari, ca. 24 km SE of Santiago on road to Nova Esperanca, Philbrick et al. 5032-5036 (ICN, MEXU, WCSU); large river that drains into the Rio Jaguari, near Ernesto Alvos, Philbrick et al. 5040 (ICN, MEXU, WCSU); Rio Taquarembo, Tupantuba, Santiago Co., Philbrick et al. 5041-5044 (ICN, MEXU, WCSU); Rio Conceicao, 11 km W of ljui, Philbrick et al. 5051, 5053, 5054 (ICN, MEXU, WCSU); Rio Porongo, 27 km NW of Soledade, Philbrick et al. 5057 (ICN, MEXU, WCSU); arroyo Tatim, 10 km S of Soledade, Philbrick et al. 5075 , 5076 (ICN, MEXU, WCSU); Rio Fao, near Pouso Novo, Philbrick et al. 5089, 5090 (ICN, MEXU, WCSU); arroyo Forquetinha, 10 km NW of Lajeado, Philbrick et al. 5091-5094 (ICN, MEXU, WCSU); Rio Moraes, 16 km S of Bom Jesus, Philbrick et al. 5137, 5138, 5140-5142, 5144 , 5145 (ICN, MEXU, WCSU); confluence of Rio Moraes and Rio das Antas, S of Born Jesus, Philbrick et al. 5146 (ICN, MEXU, WCSU); Rio Pelotas, 41 km N of Vacaria, Philbrick et al. 5157 (ICN, MEXU, WCSU); Rio Uruguay, Saito do Yucuma National Park, 1 km N of Derrubadas, Philbrick et al. 5215-5228 (ICN, MEXU, WCSU); Rio Turvo, Lara, Philbrick et al. 5242 (ICN, MEXU, WCSU); Rio Barra Grande,  Derrubadas, Philbrick et al. 5244, 5245 (ICN, MEXU, WCSU); Rio Uruguay, Tres Ilhas, Philbrick et al. 5247 (ICN, MEXU, WCSU); Rio Vila Lageado Grande, Vila Lageado Grande, Philbrick et al. 5265, 5270 (ICN, MEXU, WCSU); Rio Turvo, 3-4 km W of Daltro Filho, Philbrick et al. 5271-5274 (ICN, MEXU, WCSU); Rio Guarita, Barra Guarita, Philbrick et al. 5275-5279 (ICN, MEXU, WCSU); Rio Uruguay, ca. 3 km downstream of ltaparanga, Philbrick et al. 5281-5284, 5286, 5288, 5289 (ICN, MEXU, WCSU); Rio Pardo, Pinheirinho, Philbrick et al. 5291-5294 (ICN, MEXU, WCSU); Rio Varzea, Barreirinho, Philbrick et al. 5296-5302 (ICN, MEXU, WCSU); Rio Uruguay, Marcelino Ramos, Philbrick et al. 5304-5308, 5310-5312 (ICN, MEXU, WCSU); arroyo Teix­eira Soares, Marcelino Ramos, Philbrick et al. 5319, 5321 (ICN, MEXU, WCSU); Erechim, Philbrick et al. 5326, 5327B, 5328-5334 (ICN, MEXU, WCSU); Rio Castilhos, Getulio Vargas, Philbrick et al. 5350-5351 (ICN, MEXU, WCSU); Rio Lageado, Marcelino Ramos, Philbrick et al. 5372A, 5373, 5376, 5377 (ICN, MEXU, WCSU); Rio Teixeira Soares, Marcelino Ramos, Philbrick et al. 5378-5382 (ICN, MEXU, WCSU); Rio Teixeira Soares, Viadutos, Philbrick et al. 5383 (ICN , MEXU, WCSU); Rio Camisa, Cambara do Sul, Philbrick et al. 5556 (ICN, MEXU, WCSU); Serra des Taypes, Schwacke 2674 (C, L).-SANTA CATARINA: Rio Humboldt (town not known), Ehrhart s.n. (BM, L), 18. (L); Saito Pombinha, Pouso Redondo, Philbrick et al. 5160-5162, 5169-5176 (ICN, MEXU, WCSU); Rio Tafona, ca. 16 km W of center of Blumenau, Philbrick et al. 5177-5180 (ICN, MEXU, WCSU); Rio Sao Luis, small river that drains into W side of Rio Itajai, 3 km S of Apiuna, Philbrick et al. 5184, 5185 (ICN , MEXU, WCSU); small river that drains into Rio ltajai do Norte, 10 km from lbirama, Philbrick et al. 5186 (ICN, MEXU, WCSU); Rio Surubim, 8 km from center of Concordia, Philbrick et al. 5387 (ICN, MEXU, WCSU); Rio Vacutinga, Concordia, Philbrick et al. 5391-5395 (ICN, MEXU, WCSU); Rio Engano, Conc6rdia, Philbrick et al. 5400 (ICN, MEXU, WCSU); Rio Irani, Seara, Philbrick et al. 5404, 5406 (ICN, MEXU, WCSU); Rio Irani, ca. 15 km E of Chapeco, Philbrick et al. 5415, 5421, 5422 (ICN, MEXU, WCSU); Rio Chapecozinho, waterfall called Cascata Manela, Xanxere, Philbrick et al. 5440, 5444, 5445, 5452 (ICN, MEXU, WCSU); Rio Chapeco, Quedad do Rio Chapeco, 5 km W of Abelardo Luz, Philbrick et al. 5466B (ICN, MEXU, WCSU); Rio Jacutinga, 10 km W of Aqua Dulce, Philbrick et al. 5475, 5476, 5478-5480 (ICN, MEXU, WCSU); Rio ltajai-Acu (Rio ltajai Oeste), lbirama, Philbrick et al. 5491-5493 (ICN, MEXU, WCSU); Rio Apiuna, Apiuna, Philbrick  et al. 5501, 5502, 5505, 5507 (ICN, MEXU, WCSU); Rio ltajai, ca. 15-20 km upstream  (W) of center of  Blumenau,  Philbrick  et  al. 5512 (ICN,  MEXU, WCSU); Rio ltajai, Ascurra, Philbrick et al. 5513-5515 (ICN, MEXU, WCSU); Rio ltajai, border of Ipiuna and lbirarna, Philbrick et al. 5516, 5521-5523 (ICN, MEXU, WCSU); W side of Rio Itajai, confluence of Rio Itajaf and Rio Itajai del Norte, Ibirama, Philbrick et al. 5528-5536 (ICN, MEXU, WCSU); Apiahy, Rocha 272 (C); Gar­cia brook, near Blwnenau, Schenck 187 (L); Blwnenau, Schenck 1353 (C (spirit), L); Rio ltajahy, Schwacke 5053 (C, L); 2 km W of Rio Capetinga on road to Dionisio Cerqueira, Smith et al. 9619 (L); Rio ltajahy do Oeste, above Ibirarna, Smith et al. 7589 (L, US).-SAO PAULO: Rio lguape, lporanga, Glaziou 3135 (G, L); Rio lguape, [col­lector unknown] s.n. (C). Paraguay. Between Rio Apa and Rio Aquidaban, near Caballero-rice, Fiebrig 4990 (G, L, BM). Uruguay. SALTO: Rio Negro, Berro 281 (C); Salto Grande, Berro 3328, 5159-5160 (C); without lo­cality, Berro 3394 (C); Barra de Vera, Berro 5157 (C, L); Salto Chico, Berro 5170 (C); Rio Uruguay, Salto Chico, Hener 1708 (B, G, GH, L, MO, NY, RB, S, U, US); Rio Uruguay, Salto Grande, Osten 2903 (C, L); Rio Uruguay, Salto Chico, Depto. Salto, Tur et al. 2102 (LP, MEXU, WCSU). 

Podostemum rutifolium subsp. rutifolium is readily distinguished from all other species (except subsp. ricciiforme, see below) when ample material is available. The leaf divisions  of P. rutifolium subsp. rutifolium arise  in  the  same  plane  as  those  of the next successive division (2-dimensional), and the ultimate leaf divisions are flat in cross section. Stipules are divided into two apical teeth, and capsules have prominent ribs. 

When material is limited, P. rutifolium subsp. rutifolium and P. comatum can be dif­ ficult to separate. When flowering material is available the species are distinguished by the monomorphic (P. rutifolium) versus dimorphic (P. comatum) stems. Yet, when only small vegetative plants are available, it is difficult to distinguish the taxa; both have similar leaves and stipules when young. 

Warming (1899, p. 127) described Podostemum ostenianum based on Osten 2903. Two corresponding specimens are deposited in C, one is a pressed specimen and the other is in spirit Gar no. 11454). We select the pressed specimen as the lectotype.