BETULACEAE. Betula alba: Nelson, Hanmer State Forest, 400 m. CONIFERAE. Cupressus macrocarpa: Auckland, Orewa, 30 m. FAGACEAE. Fagus sylvatica: Canterbury, Christchurch Botanic Gardens. Nothofagus cliffortioides: Wellington, Oturere River, Mt. Tongariro, 1,200 m; Mangatorutoru Valley, Mt. Ruapehu, 1,000 m. Nelson, Lake Rotoiti, 700 m. PAPILIONACEAE. Cytisus scoparius: Wellington, Kelburn, 120 m; Turangi, 400 m. Marlborough, Kaikoura, 10 m. Canterbury, Riccarton, 10 m. South Australia, Adelaide. Lupinus arboreus: Auckland, Piha, 30 m. Wellington, Feilding, 25 m. Robinia pseudoacacia: Auckland, Mt. Eden, 50 m. Ulex europaeus: Swanson, 270 m. PITTOSPORACEAE. Pittosporum crassifolium: Auckland, Mt. Albert, 35 m. ROSACEAE. Cotoneaster vulgaris: Auckland, Owairaka, 85 m. Crataegus oxyacantha: Auckland, Buried Village, Wairoa, 450 m. Cydonia oblonga: Hawke's Bay, Twyford, 10 m. Eriobotrya japonica: Auckland, Mt. Albert, 60 m. Prunus armeniaca: South Australia, Clarendon. Prunus cerasus: South Australia, Beaumont, Adelaide. Prunus domestica: Auckland, Te Aroha, 35 m. Canterbury, Christchurch. Prunus lusitanica: Canterbury, Christchurch, 15 m. Prunus persica: Wellington, Weraroa, 25 m. Pyrus communis: Auckland, Henderson, 20 m. Nelson, Motueka, 10 m. Pyrus malus: Auckland, Te Papa; Mt. Albert; Owairaka; Mt. Eden. Hawke's Bay, Havelock North; Twyford. Wellington, Turakina Valley, 60 m; Greytown, 30 m; Tiritea, 10 m. Nelson, Appleby, 35 m. Rubus idaeus: Wellington, Greytown; Feilding. Canterbury, Christchurch. SALICACEAE. Populus nigra var. italica: Auckland, Wellsford, 120 m; Thames, coast. Populus tremula: Wellington, Palmerston North. Salix fragilis: Auckland, Mt. Albert. SAXIFRAGACEAE. Escallonia vulgaris: Auckland, Mt. Albert, 35 m. Otago, Edendale.

Hymenophore annual, membranous, pileate, sessile. Pilei effused-reflexed or flabelliform, solitary or more usually laterally connate and imbricate, sometimes with a broad resupinate base and reflexed margins, occasionally resupinate, 3-10 mm radius, 3-15 mm wide, when connate forming linear areas to 20 cm long; pileus surface coarsely tomentose, concentrically sulcate and zoned, usually straw colour or tan, sometimes dingy grey, occasionally with denuded zones; margin thinning out, concolorous, entire, inturned; hymenial surface even, sometimes scantily rugulose, ochre, pallid plum or purple, occasionally creviced when old. Context white, 0.3-0.5 mm thick, a dense layer of radiately arranged parallel hyphae with a loosely intertwined zone beneath the hymenium containing vesicles, and a coloured cortex from which arise the abhymenial hairs; skeletal hyphae 3.5-4 µm diameter, walls 0.5-1 µm thick; generative hyphae 2.5-3 µm diameter, walls 0.2 µm thick, with clamp connections. Vesicles developing in a zone beneath the hymenial layer, arising from generative hyphae, pyriform, 12-18 µm diameter, carried on stout pedicels. Hymenial layer to 50 µm deep, a dense palisade of basidia, paraphyses, and sometimes paraphysate hyphae. Basidia subclavate, 16-24 x 5-6 µm, bearing 4 spores; sterigmata slender, erect, to 6 µm long. Paraphyses subelavate, 12-18 x 4-5 µm. Cystidioid hyphae absent. Paraphysate hyphae cylindrical, to 5 µm diameter, projecting to 35 µm. Spores elliptical, or with one side slightly flattened, obliquely apiculate, 5.5-8 x 2.5-3.5 µm, walls smooth, hyaline, 0.2 µm thick.

DISTRIBUTION: Cosmopolitan.

HABITAT: Crowded and often imbricate upon living or dead trunks and branches.

Readily recognised by the zone of pyriform vesicles beneath the hymenial layer, coarsely tomentose small pilei, often connate and imbricate, dimitic hyphal system with clamp connections in the generative hyphae, and small elliptical, obliquely apiculate spores. Vesicles are readily seen in growing specimens, but in old material collapse and lose their contents or disappear, then leaving cavities in the context. Occasional vesicles are flexuous-cylindrical, traverse the hymenial layer, and simulate gloeocystidia. A coloured cortex is present beneath abhymenial hairs, as in S. hirsutum, but cystidioid hyphae are wanting. Paraphysate hyphae are present in some collections, absent from others, so are without specific significance. The hyphal system is dimitic. Skeletal hyphae, although of about the same diameter as generative, differ in that walls are thicker, septa scanty, and clamp connections wanting. Commonly some shade of purple, the hymenium often exhibits other colours, such as ochre, pallid plum, or grey. In some plants the context, and especially the hymenial layer, appears zoned, the condition probably representing periods of seasonal growth. S. purpureum induces a silver leaf disease of many cultivated fruits, in New Zealand being common on apples, apricots, cherries, gooseberries, peaches, pears, plums, and raspberries. Although usually found in introduced hosts, it is not confined to these since in the herbarium are collections from endemic New Zealand plants, two on branches of Nothofagus cliffortioides, a third on stems of Pittosporum tenuifolium. In most collections spores are 5.5-6 x 2.5-3 µm but in several specimens may reach a length of 8 µm. Large-spored forms are not associated with any other noteworthy feature. The species was made the type of Chondrostereum by Pouzar (1959, p. 17).

TYPE LOCALITY: Europe.

Although silver blight was recorded from plum trees in New Zealand by Blackmore (1894), the relationship with the fungus Stereum purpureum was not proved until 1902, by Percival, working in England. Cunningham (1922a) (1922c) stated that S. purpurerun occurred throughout New Zealand in both stone and pip fruit orchards; it caused the greatest losses in apricot and peach orchards. In a survey carried out in 1953, Watts (1954) showed that losses due to silver leaf in stone fruit were high. Even today it is still a major problem in stone-fruit orchards, where losses can be high even in trees five to six years old (Anon., 19656). The fungus has a wide host range, but silvering symptoms are not produced in all host plants. As it occurs commonly on introduced hosts, it seems likely that the disease was introduced with nursery stock of a host plant.