Nephrolepis pumicicola var. pumicicola, (F. Ballard) Hovenkamp & Miyam

Hovenkamp PH & Miyamoto F, 2005, A conspectus of the native and naturalized species of Nephrolepis (Nephrolepidaceae) in the world, Blumea 50, pp. 279-322 : 297

c. var. pumicicola (F. Ballard) Hovenkamp & Miyam ., comb. nov. - Map 3b

Nephrolepis pumicicola F. Ballard (1955) 467. - Type: Keay 28655 ( K).

Differs from the type variety: Rhizome thin, upright, up to 10 cm high, fronds stiffly erect, narrow, to 120 by 3-3.5 cm; pinnae perpendicular to rachis.

Distribution - Africa: Sao Tomé, Cameroon.

Habitat & Ecology - At low elevations to 1500 m, terrestrial, often in crevices of young volcanic rocks.

Note - This variety is restricted to the Gulf of Guinea. It is relatively easy to recognize when compared with the in Africa widespread species N. undulata by its perennial habit, the stem-forming rhizome (but this may not be evident in all specimens) bearing rigidly erect fronds with numerous, small pinnae at right angles to the plane of the rachis. None of these characters provide a clear basis for a distinction as a separate species, as all occur to varying degrees in N. cordifolia from other regions. Moreover, some specimens also collected on lava show a more relaxed habit, with less distinctly horizontal pinnae and a less stiffly erect habit, and thus are closer to typical N. cordifolia (e.g., Benl & Benl FP 54, Fernando Po; Mildbraed 10678). For these reasons, we include this as a variety in N. cordifolia . However, a number of collections from the Virunga Mountains ( Congo) include plants forming small tufts ( Burtt 3280, K, "frequent inside crater") as well as plants with the typical rhizome of N. undulata ( Burtt 3117, K, "lava plains"). Clearly, more detailed investigations are necessary to decide whether N. pumicicola is here rightly included in N. cordifolia , or whether it should be included, as a perennial variety, in N. undulata.