Ascostromata (Figs 1, 2) 120-160 µm in diam., globose, immersed, subcuticular, with protruding, setose ostiole; black, scattered amphigenous. Ascostromatal wall 10-14 µm thick, cells at the surface (Fig. 3) angular, thin-walled, 7-10 µm in greatest dimension, translucent brown by transmitted light; cells of the ascostromatal wall in longitudinal section (Fig. 2) elliptical, 7-10 x 5-7 µm. Ascostromatal setae (Figs 1, 2) 20-60 µm long, 5-7 µm basally, tips subacute, brown, erect, unbranched, with 0-2 septa, arising from the cells of the ascostromatal wall around the ostiolar opening. Ostiolar canal non-periphysate. Asci (Fig 4) obclavate to broadly cylindrical, 45-55 (-65) x 9-10 (-12) µm, bitunicate, 8-spored, ascospores forming throughout the length of each ascus, uniseriate above biseriate below. Pseudoparaphyses septate, branched, hyaline, 2-3 µm wide. Ascospores (Fig 5) ellipsoid to obovoid, 10-14 x 4-5 µm, two-celled, upper cell longer, broader, and more rounded than the tapering lower cell, constricted or not at the septum, smooth, yellowish by transmitted light.
Mycelium living in cells of the leaf mesophyll and palisade tissues, translucent brown by transmitted light, forming scattered, subcuticular pseudoparenchymatic masses; cells of the hyphae c. 4 µm thick, cells of the pseudoparenchymatic masses rectangular, 7-10 µm in greatest dimension. Conidiophores (Figs 10, 11) 50-110 µm x 5 µm thick basally, growing through the cuticle, solitary or in fascicles of a few, straight, macronematous and micronematous, simple, olivaceous to brown. Conidiogenous cell (Fig. 6) terminal, polyblastic, sympodial, cicatrised; old conidial scars thickened, crowded, giving the conidiophore a nodular appearance. Conidia solitary or in short, dry, unbranched chains, fusiform to cylindrical, rounded or truncate at the apex, truncate at the base, with one basal scar and 1-3 apical scars, 0-1 septate, yellowish, smooth or minutely spinulose, (8-) 10-12 (-15) x 3.5-4.5 µm.
characteristics in culture: in 2 weeks at 20°C under natural light 1-1.5 cm in diam., velvety, raised, "olivaceous gray" (Rayner 1970), margin undulate; hyphae 3-5 µm wide, septate, smooth, with frequent intercalary or terminal, thin-walled, 7-10m wide, globose swellings. Conidiophores (Figs 7, 8) not obvious, produced behind the margin of the colony, arising from hyphae, straight, macronematous and micronematous, yellowish to brown, septate once near the base, 25-40 µm long x 3-4 µm thick basally. Conidiogenous cell (Fig. 8) terminal, polyblastic with 1-4 crowded scars. Conidia (Fig. 9) held in short, simple or branched, dry chains, 1-2 celled, cylindrical, (10-) 13-17 (-25) x 3-4 µm, with a prominent scar at each end, yellowish, smooth or minutely spinulose. Ramoconidia present, with one, large, basal scar and two, small, terminal scars 16-20 x 4-5 µm otherwise as the conidia.

Distribution: known only from the type locality.

Habitat: on fallen, overwintered leaves of Malus sylvestris cv. 'Dougherty'.

Ascostromata 120-160 µm diametro, globosa vel conica, ostiolo papilliformi, setulis aculeatis ornato, pseudoparaphysati. Asci 45-55 x 9-10 µm, bitunicati. Ascosporae 11-14 x 4-5 µm infra medium septatae, flavidae. CONIDIAL STATE: Fusicladium sp.Holotypus: PDD 32263 (ISOTYPUS: IMI 186580). Paratypi: PDD 31846 (IMI 175660), PDD 32264 (IMI 186581).

Etymology of the specific epithet: refers to the protruding ascostromatal setae that give the surface of infected leaves a roughened appearance when seen at low magnification.
Notes: isolates derived from 13 solitary ascospores were combined in pairs on apple leaf (cv. 'Dougherty')-decoction agar (Nüesch 1960) in all possible combinations in 9-cm glass petri dishes and incubated in darkness at 8°C. They were intermittently exposed to normal room light (fluorescent + daylight) for several months. No ascocarps formed.
Work is continuing to determine whether this species is pathogenic to apple and/or peach trees.
Discussion: Kienholz (1944) reports finding Mycosphaerella tulasnei (Janczewski) Lindau in leaves of apple and pear. Its bicellular, hyaline ascospores measure 11-29 X 4-9 µm and usually become 3- to 4-celled during germination. Mycosphaerella tulasnei has a Cladosporium conidial state. Venturia asperata was compared with Kienhoiz's specimens of M. tulasnei (BPI) and the two species were found to be distinct.
Filamentous pseudoparaphyses occur in the developing locule of V. asperata before ascal elongation and the asci form in a hymenium. The presence of bitunicate asci arising among pseudoparaphyses, an ascal hymenium (Fig. 2), lightly pigmented, bicellular ascospores, and setose ascostromata confirm the venturiaceous nature of this species.
Venturia asperata and V. inaequalis are the only known species of Venturia on apple. The ascospores of V. inaequalis are unequally bicellular, the upper cell of each spore being much shorter and wider than the lower. The Spilocaea conidial state of V. inaequalis is distinct from the Fusicladium state of V. asperata and produces annellate conidiophores both in nature and in cultures derived from solitary ascospores.
Venturia asperata is very closely related to both V. pirina Aderhold, the cause of pear black spot, and V. carpophila Fisher, the cause of peach scab. The ascospores of V. pirina measure 14-20 x 4-8 µm and the lower cell of the ascospore is much smaller than the upper than is the case with V. asperata. The conidia of the Fusicladium state of V. pirina measure 17-18 x 8-10 µm, are produced singly, and are broadly fusiform with a truncate base; they have only one basal scar. Venturia pirina is found only on Pyrus spp.; Menon (1956) inoculated leaves of one-year-old apple seedlings with V. pirina but could not infect them. Venturia pirina has been illustrated by Sivanesan (1974).
It is difficult to distinguish between V. asperata and V. carpophila on the basis of ascosporal morphology alone. The measurements of the ascostromata of both species overlap. The ascostromata of V. carpophila are described as being glabrous whereas the hairs on the ascocarps of V. asperata are distinct. The ascospores of V. carpophila measure 12-16 x 3-5 µm and are thus slightly longer and narrower than those of V. asperata (10-14 x 4-5 µm). The two species are distinguishable by the position of the ascosporal septum which is median in V. carpophila and submedian in V. asperata.
As with their perfect states, the Fusicladium conidial states of V. asperata and V. carpophila are difficult to distinguish. Both are Cladosporium-like in culture and Fusicladium-like in nature. The conidia of V. carpophila measure 12-20 x 4-5 µm whereas those of V. asperata measure 10-12 x 3.5-4.5 µm. After 2 weeks growth on malt extract agar the colony of V. carpophila is 0.5-1 cm in diam. whereas, under the same conditions, that of V. asperata is 1-1.5 cm.
The Fusicladium state of V. carpophila is cosmopolitan and has been recorded on peach, apricot, plum, and almond. The perfect state is known only from the type collection made in Australia on apricot leaves. Venturia carpophila has been illustrated by Fisher (1961) and Sivanesan (1974).
The conidial states of V. asperata and V. carpophila could be accommodated in either Fusicladium or Cladosporium. In culture the conidiophores are of determinate length and the conidia are held in short, branched chains. In this aspect they would be classified as Clado-sporium, sensu Ellis (1971). In nature the conidia are produced singly or in short chains as blown-out ends of successively produced growing points, the conidiophore lengthening with age. This morphology is characteristic of Fusicladium, sensu Hughes (1953). Because the conidial state in nature is Fusicladium-like it should be treated as Fusicladium and not Cladosporium.

Holotype: NEW ZEALAND-Auckland Province, Waitemata County, Oratia (Plant Diseases Division, DSIR) Research Orchard, on dead leaves of Malus sylvestris cv. 'Dougherty', Brook, Samuels 73-188 & Manning, Aug. 1973 (PDD 32263, 1SOTYPE: IM1 186580). PARATYPES: same collecting data, PDD 31846 (IMI 175660); PDD 32264 (IMI 186581).