ULTRASTRUCTURE OF THE ASCUS APICAL APPARATUS IN LEOTIA-LUBRICA AND SOME GEOGLOSSACEAE (LEOTIALES, ASCOMYCOTINA)

The ultrastructure of the apical apparatus and lateral ascus wall is c ompared in Leotia lubrica and five species currently placed in the Geo glossaceae. The lateral ascus wall consists of two layers, of which th e inner one increases in thickness in the apical apparatus. Considerab le differences in substructure of both layers are described. On the ba sis of general morphology of the apical apparatus, structure and PA-TC H-SP reactivity of the apical thickening and annulus, and occurrence o f an annular protrusion four main categories are distinguished. A reac tive annulus is demonstrated in the apical apparatus of all species, i ncluding L. lubrica. The species studied are arranged as follows: Cate gory 1a. Geoglossum nigritum and G. cookeianum; 1b. Trichoglossum hirs utum; 2. Leotia lubrica; 3. Microglossum viride; 4. Mitrula paludosa. Most fundamental is considered the position of the annulus in the apic al thickening, either fully (category 1) or partly (2-4) occupying the apical thickening, either associated with an annular protrusion (3, 4 ) or not (1, 2). The data on the ultrastructure of the ascus apical ap paratus and lateral wall, and mode of dehiscence indicate that L. lubr ica takes an isolated position, distant from the other Leotioideae (in cluding Ombrophiloideae) and the Geoglossaceae. Geoglossum, Trichoglos sum, and Microglossum can best be maintained as separate genera in the family Geoglossaceae. The ultrastructural data of M. paludosa indicat e closer affinity with Sclerotiniaceae than with Geoglossaceae.