Serpocaulon

Kessler, Michael, Smith, Alan R., Øllgaard, Benjamin, Matos, Fernando B. & Moran, Robbin C., 2023, Prodromus of a fern flora of Bolivia. XLII. Update I., Phytotaxa 630 (3), pp. 183-210 : 198-199

Key to the Bolivian species of Serpocaulon

1 Blades simple ................................................................................................................................................................. S. levigatum

- Blades pinnatifid to 1-pinnate .......................................................................................................................................................... 2

2 Blades distally pinnatifid .................................................................................................................................................................. 3

- Blades fully pinnate, each with a conform apical pinna ................................................................................................................. 15

3 Rhizomes long-creeping; rhizome scales scattered, covering <10% of the rhizome surfaces (except at the apices) ...................... 4

- Rhizomes short- to long-creeping; rhizome scales dense, covering 30–100% of rhizome surfaces ................................................ 6

4 Veins mostly or partly free; rhizomes 1.5–2.5 mm diam., brown to black; rhizome scales 1–2 mm long, attenuate, brown, sometimes spreading ............................................................................................................................................................................. S. funckii

- At least one row of closed areoles on each side of the costae; rhizomes 2–3 mm diam., glaucous; rhizome scales 1 mm long, rounded, dark brown, appressed ....................................................................................................................................................... 5

5 Rhizomes 2–5 mm diam.; rhizome scales rounded to elliptic, appressed; blades lanceolate, truncate to slightly reduced and with a decurrent wing at the base, densely pubescent along rachis abaxially, membranaceous to papyraceous ................. S. dasypleuron

- Rhizomes 1–3 mm diam.; rhizome scales deltate to lanceolate, patent at tips; blades ovate-lanceolate, truncate and broadest at the base, glabrescent or with scattered hairs on rachis abaxially .................................................................................... S. subandinum

6 Rhizome scales round to lanceolate with obtuse apices ................................................................................................................... 7

- Rhizome scales lanceolate with attenuate apices ............................................................................................................................. 9

7 Rhizome scales 1.5–3 mm wide, loosely arranged .............................................................................................. S. crystalloneuron

- Rhizome scales to 1 mm wide, appressed ........................................................................................................................................ 8

8 Sori in one row between costae and pinna margins; rhizomes 5–8 mm diam.; rhizome scales narrowly ovate, rounded to usually acute apically; leaves 25–60 cm long ........................................................................................................................... S. intricatum

- Sori in (1)2–3 rows between costae and pinna margins; rhizomes 7–11 mm diam.; rhizome scales rounded; leaves 50–110 cm long .............................................................................................................................................................................. S. latissimum

9 Phyllopodia separated 1–2(3) times the rhizome diameter; blades often folded longitudinally .................................................... 10

- Phyllopodia separated (3)5–20 times the rhizome diameter; blades usually not folded ................................................................ 12

10 Rhizome scales orange-brown, concolorous .................................................................................................................... S. australe

- Rhizome scales bicolorous with dark brown centers ..................................................................................................................... 11

11 Blades ovate, oblong-lanceolate, each with 16−35 pairs of segments; rhizome scales 3−8 × 1−3 mm, ovate-lanceolate to lanceolate, patent, bicolorous to rarely slightly concolorous, light brown at margins and dark brown toward center, apices long-acuminate, curved margins erose, dentate to ciliate ............................................................................................................................ S. lasiopus

- Blades narrowly deltate to elliptical, linear, each with 35−49 pairs of segments; rhizome scales 1–4 × 1 mm, subulate, light brown at margins and dark reddish toward center, apices caudate to acuminate, margins erose ................................................ S. wagneri

12 Rhizome scales scattered, at least behind the apex; rhizomes partly bare, glaucous .......................................... S. crystalloneuron

- Rhizome scales dense; rhizomes fully covered by scales, brown to blackish ................................................................................ 13

13 Rhizome scales more or less uniformly colored, the central cells translucent ........................................................... S. concolorum

- Rhizome scales sharply bicolorous, the central cells dark, opaque ................................................................................................ 14

14 Rhizomes 3–5(7) mm diam.; rhizome scales tightly appressed; blades lanceolate, (5–) 8–12 cm wide, proximal several pairs of pinnae somewhat shortened and deflexed .................................................................................................................... S. intricatum

- Rhizomes 5–10 mm diam.; rhizome scales somewhat spreading, appressed at the peltate base, many curving outward at the tips; blades ovate or broadly lanceolate, 12–20+ cm wide, proximal pair the largest or nearly so and spreading ................. S. vacillans

15 Sori in 1 row between the costae and the pinna margins ................................................................................................................ 16

- Sori in (1)2–8 rows between the costae and the pinna margins ..................................................................................................... 17

16 Blades deeply pinnatisect; pinnae 1.5–2(3) cm wide; areoles in 3–6 rows between costae and pinna margins ......... S. attenuatum

- Blades fully 1-pinnate; pinnae 0.7–1.3 cm wide; areoles in 1 row between costae and pinna margins .................... S. sessilifolium

17 Proximal pinnae at least partly adnate ............................................................................................................................................ 18

- Proximal pinnae not or barely adnate ............................................................................................................................................. 19

18 Costae and rachises glabrous or with 2-celled glandular hairs ........................................................................................ S. triseriale

- Costae and rachises densely pubescent, with 5- to 12-celled hairs ................................................................................. S. richardii

19 Rhizome scales ovate-lanceolate, 4–8 mm long, 2–7 mm wide, concolorous; areoles of medial pinnae 56–100 rows .......... S. rex

- Rhizome scales ± round to lanceolate, 1–11 mm long, 1–3 mm wide, often bicolorous; areoles of medial pinnae 16–50 rows ....... ......................................................................................................................................................................................................... 20

20 Rhizome scales spreading, long-acuminate, strongly clathrate, iridescent ................................................................ S. articulatum

- Rhizome scales appressed to slightly spreading, obtuse to acuminate, weakly or partially clathrate, dull .................................. 21

21 Both blade surfaces densely pubescent, with spreading, hyaline to yellowish, septate hairs 1–2 mm long ................ S. appressum

- Blades glabrous ............................................................................................................................................................................. 22

22 Rhizomes about 1 cm diam.; distal pinnae slightly adnate; 5 or 6 rows of sori on each side of the costae; pinnae 4–5 cm wide ...... ..................................................................................................................................................................................... S. articulatum

- Rhizomes <5 mm diam.; distal pinnae free to very slightly adnate; 2–4 rows of sori on each side of the costae; pinnae 1.5–4 cm wide ................................................................................................................................................................................................ 23

23 Rhizome scales roundish, obtuse to obtusely acuminate, appressed, sharply bicolorous with raised, dark centers and broad, appressed pale margins ............................................................................................................................................ S. fraxinifolium

- Rhizome scales lanceolate, acuminate, appressed to slightly spreading, weakly bicolorous with narrow pale margins .................... .................................................................................................................................................................................... S. polystichum