History of Name:
Laccaria amethystina

Agaricus amethystinus Hudson, Fl. angl. 2: 612, 1778; non Agaricus amethystinus Scopoli, Fl. carn. 2: 437, 1772 (=Cortinarius sp.); nec Agaricus amethystinus Schaeffer, Fung. Bavar. Palat. nasc. 4: 24, 1774 (=Cortinarius traganus). Laccaria amethystina Cooke, Grevillea 12: 70, 1884. Collybia amethystina (Cooke) Quélet, Fl. mycol. France: 237, 1888. Clitocybe amethystina (Cooke) Peck, Annual Rep. New York State Bot. 50: 128, 1897.
Agaricus amethysteus Bulliard, Herb. France: Pl. 198, 1784 (= A. laccatus Schaeff., Fung. Bavar. Palat. nasc. 4: 8, 1774). Omphalia amethystea (Bulliard) S. F. Gray, Nat. arr. Brit pl. 1: 614, 1821. Agaricus laccatus var. amethysteus (Bulliard) Berkeley & Broome., J. Linn. Soc., Bot. 11: 518, 1871. Russuliopsis laccata var. amethystea (Bulliard) J. Schroeter in Cohn, Krypt.-Fl. Schlesien 3(1): 623, 1889 (erroneously written 'amethystina') Laccaria amethystea (Bulliard) Murrill, N. Amer. Fl. 10: 1. 1914.
Laccaria calospora Singer, Beih. Sydowia 7: 7, 1973.
Type: ENGLAND, Devon, Dartmoor, Two Bridges, Whistmans Wood, 6 September 1971, D. N. Pegler s.n. (as L. amethystea) (K!, neotype fide Mueller & Vellinga, 1990).

Species Synopsis:

Pileus mostly 5-32 mm broad, strongly hygrophanous, bright grayish purple when fresh, fading to buff. Lamellae purple. Stipe concolorous; basal mycelium violet, fading white. Basidia 4-sterigmate. Cheilocystidia large (often up to 60 X 12 µm), undifferentiated to clavate, often very abundant. Basidiospores mostly 7-10 µm diam (excluding ornamentation), globose, echinulate; spines 1.4-2.8 µm long, > 1.2 µm wide at base. Eastern North America, associated with oaks, beech, and other Fagaceae.

Habitat and Distribution:
Solitary to scattered, occasionally caespitose; associated with Quercus and Fagus in temperate deciduous or mixed deciduous coniferous forests of eastern North America and Europe, under species of Quercus in Central America and northern South America. See Specimens Examined for the list of specimens studied.

Observations:

Laccaria amethystina can be distinguished from the other North American "purple" Laccaria (L. amethysteo-occidentalis and L. vinaceobrunnea) by its small size and stature, bright grayish purple basidiomata that fade directly to buff, and globose, coarsely echinulate basidiospores.
No tissue cultures of L. amethystina were obtained during this study. Homokaryotic and reconstituted dikaryotic isolates were violet on MMN and PDA and grew moderately fast (radius at week 6 = ± 50 mm).
Homokaryotic isolates of L. amethystina were intersterile with isolates of other taxa including L. amethysteo-occidentalis and L. vinaceobrunnea. One North American isolate and one Swedish isolate of L. amethystina were included in RFLP analyses (Gardes et al., 1990, 1991a). These two isolates had different RFLP patterns indicating that genetic divergence may have occurred between North American and Swedish populations of L. amethystina. However, the amount of intrapopulation variation is not known since only one isolate was examined from each population.
Mueller and Vellinga (1986, 1990) discussed the controversy that has persisted in the literature as to the correct name for this taxon. Most workers use the name L. amethystina, however, Murrill (1914), Dennis et al. (1960) and others have used L. amethystea (Bulliard) Murrill for this species. Cooke's name is the earliest valid name for the taxon.
Laccaria gomezii Singer & G. M. Mueller (Mueller and Singer, 1988) grows sympatrically with L. amethystina in Costa Rica and Colombia. Collections of L. gomezii are characterized by having purple basidiomata that quickly turn vinaceous brown and then brown; adnate to decurrent, close to crowded, thin lamellae; and subglobose to ellipsoid basidiospores.
Laccaria amethystina appears to be restricted to temperate deciduous or mixed coniferous-deciduous forests in eastern North America, and Europe and to neotropical Quercus forests in Central America and Colombia. Lahaie (1981) did not report material of L. amethystina from boreal coniferous forests in Canada. Mueller (1991a) reported collections of this taxon from southern Sweden.

Macromorphology:

Pileus 5-32 (-53) mm broad, convex to plane, often depressed, not striate or striate, occasionally translucent-striate when fresh, finely pruinose to fibrillose, occasionally becoming finely fibrillose-scaly, strongly hygrophanous, bright grayish purple when fresh (near "Heliotrope-Slate" or "Dark Slate Violet 1"), fading to buff ("Vinaceous-Gray," "Pale Ochraceous-Buff" or "Light Buff"); margin inrolled to decurved, entire to undulate, occasionally eroded; context up to 3 mm thick at disc, tapering to margin, concolorous with surface. Lamellae sinuate to arcuate, subdistant to distant, up to 5 mm broad, thick, subconcolorous with pileus ("Heliotrope Slate" or "Vinaceous-Drab"). Stipe 6-58(-70) x 1-7 mm, equal, subclavate or slightly bulbous, dry, fibrillose, longitudinally striate, concolorous with pileus. Basal mycelium hygrophanous, violet becoming white. Basidiospores white or very pale violet in mass.

Micromorphology:

Pileipellis of interwoven hyphae with scattered fascicles of ± perpendicular hyphae or with scattered individual ± perpendicular hyphae; fascicles composed of 10-20 hyphae; terminal cells of perpendicular hyphae 23 73.5 x 6.5-17 µm, filamentous, clavate, broadly clavate, capitate or ventricose-rostrate, walls up to 0.5 µm thick, vinaceous brown in young specimens, light yellowish brown in mature specimens; contents concolorous with hyphal walls. Pileus trama tightly interwoven, morphologically undifferentiated, hyaline, light yellowish brown or vinaceous brown. Lamellar trama parallel to subparallel; hyphae mostly 3.5-16 µm diam, thin-walled hyaline to light yellowish brown or vinaceous brown; cells barrel shaped. Subhymenium morphologically undifferentiated. Basidia 30-64.5 x 8.5-14 µm, clavate, hyaline; sterigmata (2-)4, up to 10 µm long. Cheilocystidia 25.5-64(-92) x 4-12 µm, filamentous, clavate, broadly clavate or ventricose-rostrate, abundant, thin-walled hyaline. Basidiospores (excluding ornamentation) [160/11] 7-10(-10.6) x (6.4-)7-10( 10.6) µm [ = 7.7-9 x 7.7-9 µm], Q = 1-1.07(-1.12) [ = 1-1.02], globose, rarely subglobose, hyaline, echinulate; echinulae 1.4-2.8 µm long, >1.2 µm wide at base; hilar appendix 1.3-2 µm, prominent, truncate; plage present; contents occasionally uniguttulate. Basal mycelium hyphae mostly 3-12 µm diam, tightly interwoven, hyaline; cells filamentous to barrel-shaped.