Psilotum nudum

Psilotum nudum (L.) P. Beauv.
(Latin: nudus, bare, naked)

Local names: whisk fern

Terrestrial, sometimes epiphytic perennial with short-creeping, rhizoid-bearing, branched rhizomes; roots absent (but rhizoids absorptive); aerial stems erect to ascending or arching, to 25(–50) cm tall (greenhouse material often more robust), photosynthetic, dichotomously branched 3–5 times, 3(–several)-ridged; stem appendages (= enations) veinless, scale-like, minute, 0.7–3 mm long (apparently reduced leaves but veins absent); spores all of 1 kind (plants thus homosporous), produced in eusporangiate sporangia, these fused in groups of (2–)3 to form } globose, (2–)3-lobed synangia; synangia 2–3 mm wide, solitary in axils of minute stem appendages; gametophytes subterranean, with mycorrhizal fungi; chromosome number variable, n = 46–56, 104, 210 (Thieret 1993). Low woods, swamps, wet areas, wet peaty humus, and around bases of trees and stumps; Hardin Co. in s part of Pineywoods (Correll, Correll, & Rosier 123516, TEX-LL; Correll 1960b—this collection from the Big Thicket was the first in the state; Lance Rosier led Correll to the location) and Freestone Co. in the Post Oak Savannah (L.N. Lodwick 216, TEX-LL; Lodwick 1975); se U.S. from NC (Perry & Musselman 1994) s to FL w to AR, LA, and 2 disjunct locations in TX, also disjunct to AZ (Gutierrez 2007) and nw Mexico (Sonora); extremely widespread in the Americas, Africa, Asia, Australia, New Zealand, and Pacific Islands. Sporulating summer. [Lycopodium nudum L.] Grown as an ornamental in some areas, particularly Japan (Hyam & Pankhurst 1995); it can be a minor weed in greenhouses (Thieret 1993). Although extremely rare in TX, in some areas of the U.S. (e.g., FL) it can appear as a weed. The species can be epiphytic in situations such as on tree bases, stumps, old logs, or tree forks with accumulated debris (Nauman et al. 2000; Nelson 2000). The whisk broom or “leafless twig” appearance of the whisk fern is nearly unique among pteridophytes (Nelson 2000). The rare (and often transitory) occurrence of certain pteridophytes beyond the margins of their main range (e.g., Psilotum in TX) has sometimes been attributed to transport of spores by major storms or hurricanes (J. Peck, pers. comm.). Because of its rareness and limited distribution in the state, we consider this species to be of conservation concern in TX.

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