ISOLATES EXAMINED: IMI 156096 &CBS 101.69 & FRR 722, type isolate, from a mine tip with a very high surface temperature, Staffordshire, G.B., 1967, H. C. Evans; CBS 105.69 & FRR 729, from spruce chips, Skogshogskolan, Stockholm, Sweden, 1964; T. Nilsson; IMI 154253 & FRR 1170, from bagasse, Trinidad, 1971, J. Lacey.

CYA, 25^oC, 7 days - Colonies 15-25 mm diameter, plane, typically velutinous to lightly floccose, one known isolate strongly funiculose; margins entire or fimbriate; mycelium white; conidiogenesis very light to moderate, Greyish Yellow near Sand (M. 4133); exudate and soluble pigment absent; reverse dull yellow or brown. MEA, 25^oC, 7 days - Colonies 15-22 mm diameter, plane, lightly floccose to somewhat funiculose; margins entire; mycelium white; conidiogenesis moderate, colored as on CYA; exudate and soluble pigment absent; reverse pale to dark brown. G25N, 25^oC, 7 days - Colonies 3-6 mm diameter, occasionally less, characters as on CYA. 5°C, CYA, 7 days-No germination. 37^oC, CYA, 7 days-Colonies 30-45 mm diameter, sparse to moderately dense, radially sulcate, velutinous to funiculose; mycelium white; conidiogenesis light, colored as on CYA; exudate and soluble pigment absent; reverse pale to deep yellow brown. Conidiophores borne from surface or aerial hyphae, stipes ranging from 60-400 µm x 3.0-4.0 µm, with verrucose walls, bearing penicilli of variable complexity, sometimes monoverticillate (especially on MEA), commonly biverticillate but with terverticillate or quaterverticillate struc tures also usually produced; rami 15-20 µm x 3.0-4.0 µm, walls verrucose; rarnuli 10-15 µm x 3.0-4.0 µm, walls verrucose; metulae in verticils of two or three, measuring 10-20 µm x 2.5-4.0 µm, often with enlarged apices, walls verrucose; phialides 8-10 per metula, commonly 9-11 µm x 2.0-2.8 µm, with verruculose walls, narrowing gradually to long collula; conidia cylindroidal, 3.5-4.0 µm x 2.0-2.5 µm, walls smooth to verruculose, borne in disordered chains.

TYPIFICATION: Herb. CBS 101.69 was designated as holotype by Stolk et al. (1969). Herb. IMI 156096 is isotype material.
DISTINGUISHING CHARACTERS: As noted by Stolk e t al. (1969), Geosmithia argillacea is apparently closely related to G. cylindrospora. Geosmithia argillacea grows more rapidly on CYA at 25^°C and especially at 37^°C, whereas conidia of G. cylindrospora en masse are colored much darker brown. Unlike those of G. cylindrospora, phialides of G. argillacea taper gradually towards the apices.
Stolk et al. (1969) reported that Geosmithia argillaea is thermotolerant, with an optimal growth temperature near 35^oC and a maximum near 50°C. It has been isolated from hot environments such as a mine tip and wood chip piles.