Ericaceae-Neotropical Blueberries
James L. Luteyn and Paola Pedraza-Peñalosa
The New York Botanical Garden

PTEROSPORA

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     Pterospora (Ericaceae, Monotropoideae) is a monotypic genus distributed in coniferous and mountainous regions of western North America, with scattered disjunct extensions south into Mexico, and to northeastern United States and adjacent Canada.  The subfamily to which Pterospora belongs is composed of herbs which lack chlorophyll, all species having an obligate mycotrophic habit in which they appear to be indirectly parasitic on coniferous or fagaceous hosts by means of mycorrhizal fungi common to host and parasite.  They are also characterized by pollen in monads.  A single species, P. andromedea, occurs in the Neotropics, more specifically in Mexico, in forests of Pinus and Quercus at elevations of 2300-4000 m.  Flowering specimens have been collected May to Nov, but are usually found in Jul-Aug. For more information about the subfamily and genus, and its relationships, see the various papers by Wallace (1975a,b, 1977, 1995a,c).

 

PTEROSPORA Nuttall, Gen. N. Amer. pl. vol. 1: 269-270.  1818; Hemsley, Biol. cent.-amer., Bot. 2: 285.  1881;  Drude, in Engler & Prantl, Nat. Pflanzenfam. IV(1): 3-11.  1889;  Copeland, Madroño, 6(4): 97-119.      1941;  Bakshi, Ecological life history of Pterospora andromedea, Dissertation, State College of Washington, Pullman.  1958;  Wallace, Wasmann J. Biol. 33(1 & 2): 1-88.  1975a (Pterospora, pp. 63-68, map 10);  Barrios, La Familia Pyrolaceae en el Valle de Mexico, Thesis, Escuela Nacional de Ciencias Biologicas, Mexico  D.F., 1984;  Barrios, Pyrolaceae pp. 188-194, in Rzedowski & Rzedowski, Flora Fanerogámica del Valle de Mexico, vol. II.  1985;  Wallace, Fl. Neotrop. Monogr. 66: 25-27.  Type species.  Pterospora andromedea Nuttall.  Monotypic.  The following is a combined generic and specific description.

Pterospora andromedea Nuttall, Gen. N. Amer. pl. vol. 1: 69-270.  1818.  Neotype, designated by Wallace (1975a):  USA, California, Butte Co., Jonesville, 15 Jul 1931, E. B. Copeland 668, RSA; isoneotypes, CAS, DS, MO, NY, ORE, P, RM, UC.

     Roots a shallow to deeper condensed mass, finely branched with brittle, short, ultimate branches.  Inflorescence erect, racemose, 1.5-20 dm high, from root connection, 0.5-1.5 cm diam. below lowermost flower, conspicuously glandular pubescent, viscid, tough in texture due to presence of fibrous bundles, pink to reddish;  sterile bracts scattered along inflorescence, imbricate in bud protecting emerging inflorescence;  floral bracts never similar to perianth, narrow lanceolate, 0.5-2.5 x 2-4 mm, glandular pubescent, margins ciliate to irregularly cut;  pedicels recurved, 2-25 x 1-2 mm, terete, glandular pubescent, remaining recurved in fruit;  bracteoles absent.  Flowers urceolate, nodding at anthesis and in fruit, 5-merous;  calyx distinct from corolla, sepals 4-6 x 2-3 mm, lance-ovate, persistent in fruit;  corolla sympetalous, urceolate, 6-9 x 5-7 mm, mouth 2-3 mm diam., essentially glabrous, 5 lobes imbricate in bud, reflexed at anthesis, free for 1-2 mm, corolla not conspicuously saccate at base, cream to yellowish or rarely pinkish in color;  stamens 10 in two series of alternating lengths, 3-5 mm long;  filaments slender, flattened, expanded at base, glabrous;  anthers ca. 1 mm in diam., each with two dorsal awns 1-1.5 mm long, dehiscence by two gaping lateral slits;  ovary 3-4 x 4-6 mm at anthesis, glabrous, locules 5, lacentation axile, ovules numerous;  nectary of low lobes between staminal bases;  style cylindric, slender, 1-3 mm x 1 mm diam., included, conspicuously articulated with ovary, the base in a depression at apex of ovary;  stigma discoid ca. 1.5 mm diam., with 5 very shallow lobes, lacking any ring of subtending hairs.  Fruit an oblatespheroidal, loculicidal capsule, 5-10 x 7-14 mm, borne on recurved pedicel, valves dehiscing from base first;  seeds numerous, minute, less than 0.5 mm diam., including a broad, apical, thin membranous wing;  embryo and endosperm claimed to be of 30-40 cells (Terekhin, 1963) but Bakshi (1958) found the embryo to be two celled;  chromosome number: 2n=16 (Bakshi, 1958).

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     This is a version of the taxonomic treatment of Pterospora (Ericaceae: Monotropoideae) by Gary D. Wallace, modified from "Ericaceae--Part II. The Superior-Ovaried Genera (Monotropoideae, Pyroloideae,  Rhododendroideae, and Vaccinioideae p.p.)."  The full treatment including specimen citations may be see in Flora Neotropica Monograph 66: 25-27 (Wallace, 1995c).  This on-line synthesis is published with permission of The New York Botanical Garden and Gary D. Wallace.

 

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