Macroscopic feat.:

• Cap/Pileus: (17-) 35-60 (-70) mm diam, convex-umbonate becoming plane with a mammillate-papillate umbo, smooth, lubricous; margin even, translucent-striate or slightly sulcate-striate, yellowish brown (5DE5-8) to dark reddish brown (8E-F5-6), chocolate brown (6F4) or Verona Brown, or dark grayish brown (5D-F3) mainly on the umbo, hygrophanous, changing to beige or pale brownish-yellow.
• Gills/Lamellae: Sinuate, pale brown or violaceous brown (11F4-6), margin even or somewhat fimbriate, pallid or concolorous.
• Stem/Stipe: (20-) 80-130 (-175) 3 3-6 (-8) mm, hollow, equal with a bulbous base, sordid white, becoming pale brown or yellowish brown (5D-E5-8) or reddish brown (8E5-7) or fuscous reddish toward the apex, shiny or dull, silky, covered with fibrillose appressed white fibrils toward the base, texture tough-cartilaginous or subwoody, with rhizomorphs at the base, inserted up to 1/4 of the total length.
• Context: Both in pileus and stipe whitish, or reddish-brown in the base of the stipe. All parts except lamellae strongly caerulescent when cut or touched.
• Odor: Farinaceous.

Microscopic feat.:

• Basidio/Spores: Spore print Dark Violaceous Brown. (6-) 6.5-7.5 (-8) x 5-5.5 (-6.5) x 4.5-5 µm (Q = 1.25), subrhomboid in face view, subellipsoid in side view, thick-walled, walls up to 1 µm thick, yellowish-brown, with a broad germ pore.
• Basidia: (16-) 20-25 (-28) x 5-6 (-7) µm, 4-sterigmate, hyaline, vesiculose, with a median constriction.
• Pleurocistidia: (9,5-) 12-17 (-20) x (3,5-) 5-8 (-12) µm, hyaline, subventricose, subfusoid or subcylindric-moniliform, with an acute apex or short neck.
• Cheilocystidia: (16-) 18-30 (-37) x (4-) 5-8 (-9.5) µm, hyaline, subventricose, irregularly branched, with an acute apex or with a short neck.
• Subhymenium: Very thin, subcellular, with hyaline to yellowish elements, 3-6 (-8) µm, wide, finely encrusted.
• Trama: Regular, most hyphae hyaline, cylindrical or with some elements inflated, 3-24 µm wide, with fine, inconspicuous encrustations.
• Epicutis: A subgelatinized layer 8-40 µm thick, composed of repent, hyaline hyphae, 2.5-7 µm diam.
• Pileocystidia: 25-43 3 6-8 µm occasional, prostrate or erect.
• Hypodermium: With both hyaline cylindrical hyphae and subglobose elements, 2-15 µm wide, with encrusted walls. Context composed of hyaline or yellowish hyphae, some inflated and becoming subglobose, 3-24 µm wide, thin or thick-walled, up to 1 µm thick. Clamp connections common.

Habitat: Gregarious or caespitose on rich organic or sandy soil, mixed with decaying plant debris, in tropical and subtropical forests. Known only from Puerto Rico.

Studied material: PUERTO RICO, Mun. Naguabo, Luquillo Mountains, trail from Río Icacos to Río Prieto Dam, 4 Oct 1999, Laboy (PR-5772) (CFMR). Tradewinds Trail, 25 Jun 1995, Lodge, Barley & Wunderle (PR-2669) (CFMR), Lodge, Barley & Wunderle (PR-2671) (CFMR). Mun. Río Grande, Caribbean National Forest, El Yunque, Caimitillo Trail, 29 Jun 1996, Baroni 7971 (HOLOTYPE CORT; ISOTYPE XAL). Mun. Río Grande, Luquillo Mountains., La Mina Recreation Area, Mount Britton Trail, 23 May 2000, Cantrell & Salgado, ledger Cantrell PR-0022 (PR-6170) (UPRRP). MARTINIQUE, Vallée du Lorrain, Nov 1974, Fiard 87 (K(M): 84377); 4 Jun 1975, Fiard 87C (K(M): 84376). Between Gran Riniere and Anse Ceron, 17 Jan 1982, Fiard 1503 (K(M): 84375).

Discussion: Pegler (1983) considered collections of this species from Martinique to be Psilocybe caerulescens. However, even though Psilocybe caerulescens is a member of section Cordisporae, it lacks pleurocystidia and is easily separated from Psilocybe caribaea, which has abundant pleurocystidia.
Psilocybe caribaea is attractive because of its robust basidiomata, which occur in clusters. Its habit is reminiscent of Psilocybe collybiodes Singer & A.H. Smith, but that species has thin-walled ellipsoid basidiospores (Guzmán, 1983). Psilocybe caribaea is most phenetically similar to Psilocybe subtropicalis Guzmán, known from Mexico and Guatemala (Guzmán 1995). However Psilocybe caribaea can be separated from Psilocybe subtropicalis, because it possesses two types of pleuro- and cheilocystidia (recent observations on the holotype by Guzmána and Tapia).
One specimen, PR-6170, possesses slightly larger basidia 28-37 x 6-7 µm with 1, 2, 3 and 4 sterigmata and slightly longer pleurocystidia (13-) 15-24 (-26) µm. However, the differences observed in this collection appear to be reasonably expected morphological variations for Psilocybe caribaea.

source - www.mycologia.org [95 (6): 1172-1174]

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