Wright J.E. 1987. Bibliotheca Mycologia 113: 164.
Tulostoma obscurum J.E.Wright (Fig.106) apud Wright, Herrera & Guzman, Ciencia (Mexico) 27 (4-5): 118. 1972.
Etym.: The name refers to the obscure nature of the spore ornamentation.
Spore-sac up to 15 mm wide, averaging about 10 mm, generally globoseapplanate. Exoperidium indistinctly but obviously membranous, very thin, persistent in patches on the endoperidium and particularly at the base, slowly caducous in small patches. Endoperidium ochraceous tan, never completely smooth, but with remains of the thin membranous exoperidium. Mouth fibrillose-fimbriate, although this feature is not always easy to distinguish, slightly mammose; in some specimens the mouth seems to be indefinite due to erosion, and in others, it does not exist. Socket tightly appressing the stem, membrane lacerate. Gleba ochraceous to ferrugineous. Stem up to 30 x 3 mm, rugose-squamose, dark brown, later peeling off and becoming lighter to straw-colour, sometimes sulcate in the upper third, straight, but in some specimens it appears tortuose, not volvate, generally ending basally in a mycelial bulb with brown threads and some slender rhizomorphs.
Spores verrucose, although the verrucae are difficult to discern, brownish-yellowish, episporium thick, 6.8-8.5-(10) Âµm diam; some very large ones mixed with smaller ones, may have large verrucae mixed with smaller ones, granular under L.M.; under SEM the ornamentation appears as relatively small, isolated, almost globose verrucae mixed with others anastomosed in short crests. Capillitium hyaline to slightly coloured, scantily branched, septate; threads 2.4-9.3 Âµm diam, thick-walled and lumen visible to lacunar; the walls often incrusted on the outside with a granular material that is very fine and hyaline; not swollen at the septa, disjointable with blunt ends.
Habitat: sandy soil in arid regions.
Distribution: North America: S and SW United States, Mexico. Holotype: United States, Colorado, Boulder, leg. R.H.Stevens (Herb. Lloyd no 53.167, BPI!).