PHAEODISCUS, A NEW GENUS OF SCLEROTINIACEAE (INOPERCULATAE: DISCOMYCETES)

Phaeodiscus, a new genus of Sclerotiniaceae, is described with P. rhamnicola Batra as the single species. It is characterized by an ectal excipulum of subhyaline textura prismatica and textura porrecta; dichotomously branched, golden brown, aculeate paraphyses; and golden brown, narrowly ellipsoid, usually biguttulate ascospores. The two guttules fuse at maturity to form a single central guttule. The apothecia arise from pseudosclerotia colnsisting of numerous interconnected sclerotules. A number of other Sclerotiniaceae related to the new fungus are conmpared with it. THE BROWN-SPORED, inoperculate stromatic discomycete described below as Phaeodiscus rhamnicola was collected in 1960 from Mussoorie, India. The brown-pigmented paraphyses are dichotomously branched and the ultimate branches are aculeate. The subhyaline ectal excipulum consists of a textura prismatica two to three cells thick, ensheathed by textura porrecta. The medullary excipulum is primarily of textura intricata, consisting of narrow, light brown, granular hyphae. This combination of characters does not permit its inclusion in other brownspored genera of Helotiales such as Lambertella von Hoehnel (Fig. 12-17), Martinia Whetzel (1945) and Phaeociboria von Hoehnel (Fig. 18-22), of family Sclerotiniaceae, or in Velutarina Korf and Phaeangellina Dennis of Helotiaceae (Dennis, 1960b). Phaeodiscus BATRA, GEN. N. FAMILY SCLEROTINIACEAE, ORDER HELOTIALEs-Apothecia solitaris stipitata cupulata, e contextu pseudosclerotiali oriunda. Excipulum ectale bizonatum: (1) zona interiore cellulis 2-3 crassa e textura prismatica tenuitunicata subhyalina, (2) zona exteriore pallide brunnea e textura porrecta compositis. Excipulum medullosum e textura pallide brunneola intricata ex hyphis angustis granulosis efformata compositum. Hymenium brunneum; paraphyses aureobrunnea, repetite dichotomeque ramosae. Asci cylindrici octospori, poro ope liquoris melzeri pallide brunneolescentes. Ascospores aureobrunnea, ellipsoideae, unicellulares, primum guttulis 2-3, in maturitate ad guttulam solam mediam conjunctis praeditae. Apothecia arising from pseudosclerotial tissues, 1 Received for publication 19 April 1968. The author thanks Dr. R. P. Korf, Cornell University, for many helpful suggestions. The technical assistance of Mrs. Eleanor Martin is gratefully acknowledged. Miss Edith K. Cash prepared the Latin diagnoses. solitary. Paraphyses golden brown, repeatedly dichotomously branched, sometimes anastomosing. Asci eight-spored, pore staining faintly brown in Melzer's reagent. Ascospores golden brown, one-celled, with two to three guttules, which on maturity become fused into one central guttule. Ectal excipulum differentiated into two zones: (1) an inner zone of two to three cells thick, subhyaline, thin-walled textura prismatica, and (2) an outer zone of light brown textura porrecta. Medullary excipulum light brown, of textura intricata. Type Phaeodiscus rhamnicola Batra. PHAEODISCUS rhamnicola Batra sp. n.(Fig. 1-11). Apothecia solitaria e sclerotulis subepidermicis oriunda, stipitate discoidea, hymenio pallide brunneo. Discus apothecialis cupulatus in maturitate discoideus 0.50-0.75 mm diam, superficie concolori et glabra. Stipes cylindricus tenuis fragilisque, 1.0-1.5 cm longus, 200-250 u latus, etomentosus, corde medio e textura porrecta, superficie textura compacta prismatica compositis. Hymenium 144-200 ,u crassum, brunneum. Subhymenium obscurius, e textura intricata. Excipulum medullosum 21-43 , crassum, ex hyphis brunneolis granulosis 2-4,4 latis compositum. Excipulum ectale hyalinum bizonatum: (1) zona interiore subhyalina e textura prismatica interdum angulari 2-3-cellulis crassa, (2) zona exteriore pallide brunnea e textura porrecta composita, hyphis terminalibus crassitunicatis tomentum efformantibus praedita. Asci octospori primum pallide brunnei cylindrici, ad apices rotundati, graditim in basin modice latam attenuati, poro ope liquoris melzeri brunnescente, 98-128 X 8-12,u. Ascosporae fuscobrunneae, biseriatae vel irregulares, anguste ellipsoideae interdum planoconvexae, crassitunicatae, 2-3demum 1-guttulatae, conspicue verrucosae, interdum verrucis gemmiformibus 3 , altis, 2-3,u latis ornatae, 13-21 X 3.8-6.5,u. Paraphyses con-