Selaginellaceae

Zhou, Xin-Mao, Rothfels, Carl J. & Zhang, Li-Bing, 2025, Phylogeny and systematics of the New World Selaginellaceae in a global context, Phytotaxa 684 (2), pp. 147-192 : 161-162

Key to the New World genera of Selaginellaceae

1. Peltate sterile leaves with forked veins (not visible unless the leaves are cleared and the vascular tissue stained) [subfam. Mexiselaginelloideae ]....................................................................................................................... Mexiselaginella ( M. schaffneri )

1. Basifixed sterile leaves without forked veins.....................................................................................................................................2

2. Rhizophores absent, strobili cylindric [subfam. Selaginoidoideae ] ......................................................... Selaginoides ( S. spinulosa )

2. Rhizophores present, strobili tetragonal or slightly dorsiventrally complanate.................................................................................3

3. Rhizophores borne on dorsal side of stems and/or branches [subfam. Gymnogynoideae ]................................................................4

3. Rhizophores borne on ventral side of stems and/or branches, or rhizophores strictly restricted to the base of stem ........................7

4. Stems often articulate, strobili with only one or few megasporangia at base, microspore surfaces echinate or pillared ..................5

4. Stems often inarticulate, strobili with many megasporangia on dorsal and/or ventral side, microspore surfaces verrucate or striped .................................................................................................................................................................................................6

5. Plants extremely large (up to 1 m tall), stem’s vascular system actino-lectostele, megaspores ca. 1.5 mm, microspore surfaces pillared........................................................................................................................ Megaloselaginella ( M. exaltata , M. gigantea )

5. Plants normally shorter than 80 cm, stem’s vascular system haplostele, actinostele, or plectostele, megaspores smaller than 1 mm, microspore surfaces often echinate .............................................................................................................................. Gymnogynum

6. Sterile leaves strictly monomorphic and spirally arranged throughout the plants, plants creeping or erect..................... Bryodesma

6. Sterile leaves dimorphic or some slightly monomorphic on stem and four rows throughout the plant, plants often rosette-forming (except L. rzedowski with creeping rhizomes) .......... Lepidoselaginella ( L. lepidophylla , L. novoleonensis , L. ribae , L. rzedowski )

7. Plants xerophytic, often forming rosettes, rarely stems erect, rhizophores strictly restricted to the base of stem and stems tufted and curling inward when dry, megaspore surfaces coarse without clear ornamentation, microspores spherical, surface scabrate or verrucate [subfam. Pulvinielloideae ]................................................................. Pulviniella ( P. convoluta , P. gypsophila , P. pilifera )

7. Plants growing in wet habitats or rarely slightly xerophytic, erect, suberect, ascending, or creeping, rarely rosette-forming (e.g., Selaginella nothohybrida and S. pallescens ), megaspore surfaces often reticulate, rarely tuberculate or verrucate, microspores often hemispherical and surfaces often baculate or blunt echinate, rarely cristate, gemmate or verrucate [subfam. Lycopodioidoideae , subfam. Selaginelloideae ]...................................................................................................................................................................8

8. Sporophylls dimorphic or sub-dimorphic (dorsal sporophylls larger than ventral ones)........................................... Selaginella p.p.

8. Sporophylls monomorphic .................................................................................................................................................................9

9. Plant entirely creeping, sporophylls obviously reduced toward base of strobili forming a stalk.............. Valdespinoa ( V. douglasii )

9. Plant creeping, ascending to entirely erect, sporophylls in similar sizes on each side (dorsal or ventral) of strobili from base to apex...................................................................................................................................................................................................10

10. Stems often stramineous or green, megaspore surfaces often reticulate, microspore surfaces often baculate or blunt echinate, rarely gemmate or verrucate ................................................................................................................................................. Selaginella p.p.

10. Stems pale reddish at base of stems, megaspore surfaces tuberculate, microspore surfaces cristate folds.......................................... ...................................................................................................................................................................... Didiclis ( D. hoffmannii ).