The genera Melanaria and Pertusaria (Pertusariaceae) have been distinguished primarily by spore pigmentation, the spores of Melanaria being olive-green and those of Pertusaria being hyaline. The developmental stages of asci and spores of Melanaria macounii var. meizotoca Lamb closely parallel those of Pertusaria pertusa (L.) Tuck. and P. pustulata (Ach.) Duby. However, the spores of Melanaria differ from those of Pertusaria in the development of an inner, reticulate, pigmented wall layer. Immature apothecia of M. macounii var. meizotoca have a dense, possibly meristematic, layer of hyphae across the upper portion of the lacunae. In mature apothecia the dense layer was found around the ostiole. No such layer has been found in Pertusaria. Apothecial walls of Melanaria are quite thin, only 1-2k-wide in immature apothecia and 2-3k-wide in mature ones. Those of Pertusaria average 4-7M. Melanaria macounii var. meizotoca, a member of the Pertusariaceae, was described by Lamb (1954) from a collection of John Macoun from Victoria County, Cape Breton Island, Nova Scotia, Canada. Two genera of the Pertusariaceae, Melanaria and Pertusaria, are distinguished on the basis of ascospore pigmentation, those of Melanaria being olive-greenish and those of Pertusaria hyaline. Superficial examination of Melanaria leads one to believe that it could be a Pertusaria variant with dark spores. Therefore, a cytological study was undertaken to determine if the structure and sequence of ascus and ascospore development of M. macounii var. meizotoca differ significantly from those of Pertusaria. MATERIALS AND METHODS The specimens were collected in Porcupine Mountains State Park, Ontonagon County, Michigan. Materials were obtained at several different times during a 12-month period so that seasonal variations in development might be discerned. Within 2-30 hours after collection, the specimen was washed and placed in artificial light for 12 hours, then fixed in either Belling's modified Navashin's fluid or in Newcomer's fixative (Newcomer, 1953). Materials fixed in Navashins fluid were embedded in paraffin, sectioned at 7lL and stained in Heidenhain's iron hematoxy]in (Erbisch, 1969); materials fixed in Newcomer's fixative were stained in Wittmann's aceto-iron-hematoxylin and squashed (Erbisch, 1969; Wittmann, 1962). RESULTS Apothecial Development. The earliest stage found consisted of a ball of intertwined hyphae in the lower third of the thallus (Fig. 1, 11). The cells of this ball, 1 Department of Biological Sciences, Michigan Technological University, Houghton, Michigan 49931. This content downloaded from 157.55.39.92 on Wed, 22 Jun 2016 07:05:39 UTC All use subject to http://about.jstor.org/terms 490 THE BRYOLOGIST [Volume 72