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Fungi associated with Engelmann spruce and subalpine fir were studied in a high altitude area of western Wyoming. Thirty permanent plots were established and their mean stand age determined. Three age classes were delineated: young (78 years), mature (127 years), and old-age (216 years). Stand and soil parameters including density, basal area, and soil pH, P, K, Ca, organic matter, and Mg concentrations were used to define similarities in stand characteristics. Sporocarps of higher basidiomycetes and ascomycetes were collected and identified, and ectomycorrhizal root tips sampled from each plot. Pure cultures of the basidiomycetes were routinely attempted. Mycorrhizal syntheses were subsequently attempted with both tree species using successful pure cultures. Thirty-nine species of higher fungi were collected during the study. Distribution of sporocarps throughout the age classes revealed a distinct fungal flora in each age class. Greatest density of species appeared in the mature stands. Non-mycorrhizal fungi were more abundant in the mature stand while mycorrhizal species were more abundant in the old-age stand. Mycorrhizal root counts increased from young to old-age stands. Low numbers of sporocarps and mycorrhizal rootlets were collected from the young stand. It seems evident from this study that a more diverse assemblage of higher fungi is present in mature and old-age forests and a progressive increase of fungal species from young to old-age stands supports the hypothesis that fungal succession is occurring in the study area.

Morphologically and anatomically the Russulales (Basidiomycetes) are a homogeneous group of higher fungi, which contains both ballistosporic and statismosporic, agaricoid and gasteroid taxa. Spore symmetry and ability to forcibly discharge spores are therefore fundamental systematic characteristics in the Russulales. Ballistosporic and statismosporic basidiosporogenesis however, has not been critically compared. Early and late basidiosporogenesis, spore-wall tegumentation, and differentiation of the hilar appendix were ultrastructurally characterized in species selected from eight genera of agaricoid and gasteroid Russulales including: Russula, Lactarius, Macowanites, Arcangeliella, Elasmomyces, Gymnomyces, Martellia, and Zelleromyces. Six spore-wall layers are present in developing spores in all genera. Two wall layers are associated with an evanescent pellicle and four wall layers are derived from the sterigma and young spore. The amyloid portion of the spore wall in the Russulales is an electron-translucent wall layer covered by an electron-dense surface layer. Ontogeny of spore-wall ornamentation is similar in all genera, however diversity in the degree of ornamentation and amyloidity results from differentiation and intermixing of the two outermost enduring wall layers. Establishment of early spore asymmetry in both ballistosporic- and statismosporic-heterotropic basidiospores is highly correlated with the presence of a hilar appendix body. Observation of a demarcated cytoplasmic region, reminiscent of the hilar appendix body, in asymmetric sterigmata of orthotropic Russulales suggests that basidiospore morphology and symmetry are variable features in the Russulales. Late spore development subsequent to nuclear migration is similar in orthotropic and heterotropic Russulales. Orthotropic basidiospores appear to be released from sterigmata upon breakdown of the sterigmata. Heterotropic basidiospores are released while sterigmata are intact. Plugging layers develop in both the sterigma and in the hilar appendix. The hilar appendix plugging material appears to be produced by a plug-forming body which originates in the spore, and possibly controls liquid droplet formation during ballistosporic discharge. Ballistosporic discharge appears to be a conservative phenomenon in most Basidiomycetes resulting from a prescribed sequence of biochemical and developmental processes. The use of ballistospory and statismospory in distinguishing families and genera must be re-evaluated in the Russulales. Recognition of the Lactariaceae and Russulaceae is discussed.