Mycelium. Pure white. Hyphae hyaline, slender 1-2 µ wide, thin-walled, septate; cells 15-25 µ long. Sporodochia. Minute shallow cups, circular or irregular, 0.05-0.2 mm. in diameter, about 0.05-0.1 mm. deep and often confluent into larger masses. Composed of loosely arranged hyphae, arising from a compact or pseudoparenchymatous base, and terminating in a dense disk-like layer. Green at first, becoming jet black surrounded by a white rim of rather broad, thin-walled, contorted, hyaline hyphae. Conidiophores composed of fertile hyphae and phialides (Text-fig. 4). Fertile hyphae. Tinted brown, consisting of a main axis usually of three cells with branches arising irregularly from below the septa and very closely intertwined. Cells 3-13 µ long by about 2 µ wide, the terminal cell always shorter than the others. Interspersed by unbranched, sterile, dark brown, thick-walled, somewhat sinuous filaments, 3-4 µ wide and 4 µ or more in length (the walls of which frequently appear verrucose). Phialides. Subhyaline to pale olive green, greenish brown in the mass, arising terminally or from a geniculation of the parent cell, very slenderly clavate, rather thick-walled, 7-22 x 3 µ. The terminal phialides short, straight or slightly flexuose, the lateral ones longer and bent sharply near the base, the whole thus forming a closely packed, even, hymenial layer. Conidia. Small, continuous, sub-fusoid, guttulate, broadest slightly below the middle, with the apex pointed and the base terminated by a minute stalk-like protuberance less than 1 µlong. Epispore at first smooth becoming fluted, usually with about fifteen ridges arranged longitudinally and often somewhat spirally. At first sub-hyaline, when mature smoky olive brown, 7 x 2.5-12 x 3.5 µ, average 9-6 x 3 µ.

Hab. Clay soil. New Zealand.

Mycelium ex hyphis hyalinis, tenuiter tunicatis, septatis 1-2 µ diam. compositum. Sporodochia minuta, tenuiter cupuliformia, orbicularia vet irregularia, 0.05-0.2 mm. diam. saepe confluentia, primo viridia demum aterrima, margine albido ex hyphis contortis, hyalinis, tenuiter tunicatis, aliquanto latioribus composito. Setae rarissimae. Conidiophora ex hyphis fertilibus phialidibusque composita. Hyphae fertiles brunneo-tinctae, praecipue 3-septatae, irregulariter infra septa ramosae, ramis sursum dense intertextis, discum obscurum efficientibus; adsunt quoque hyphae steriles, non ramosae, atrobrunneae, inter hyphae fertiles crescentes. Phialides e subhyalino olivaceae, vet terminates vet e geniculo cellulae primogenitae oriundes, tenuissime clavatae, 7-22 x 3 µ. Phialides terminales semper ceteris breviores. Conidia subhyalina deinde olivaceo-brunnea, continua, subfusoidea, apice acuta, basi minute apiculata, episporio primo laevi demum longitudinaliter striato ornata, 7 x 2.5 ad 12 x 3.5 µ (av. 9.6 x 3 µ).

Material studied and characteristic features
This fungus was originally isolated by J. C. Neil (No. 582) from a clay soil in New Zealand. A sub-culture of Neil's isolate was obtained through the Imperial Mycological Institute and this, together with subsequent transfers, has formed the basis of the present description.
The sporodochia of this species (Text-fig. 5) are superficially indistinguishable from those of M. roridum, the white fringe being composed of twisted hyphae among which the presence of setae is very exceptional. Only once have any setae been found among the many hundreds of sporodochia examined (Text-fig. 1C).
Microscopically this species is readily distinguished by its striate, or fluted, conidia which are generally sub-fusoid though occasionally approximating to rod-shaped. It is further distinguishable from either M. roridum or M. verrucaria by the dark colour of the hymenial layer, and by the characteristic dark brown sterile filaments which are frequently found interspersed among the fertile hyphae, often extending beyond the general surface of the disk.

Hab. Ex terra argillacea sub agro pascuo, in Nova Zealandia in 1937 isolatum (J. C. Neil 582) et in agaro excultum et descriptum. Pars exsiccata in Herb. I.M.I. deposita sub. no. 1526 est typus.