ASCOCARP AND SPORE ONTOGENY IN 2 SPECIES OF SPHAEROPHORUS (CALICIALES)

Two different ascocarp ontogenies have been demonstrated in Sphaerophorus (Caliciales). A globose primordium arises in both species investigated. In S. globosus, the primordium wall encloses the whole structure during the hymenium development, although a weak differentiation of the basal part takes place, while in S. tener the wall is clearly differentiated into a watchglass-like basal part and a cap-like apical part not in contact with the basal part. In S. globosus, the cover disintegrates during the mazaedial development. In S. tener, the cover persists until the mazaedium is well developed, and is then shed, most often in one piece, thereby exposing the spores. The mechanism of the shedding and the possible biological consequences of the specialized ascocarp ontogeny in S. tener is discussed. The spore ontogeny of S. tener has also been investigated. No ornamentation is deposited on the spore surface until the spores are liberated from the asci. The spore ontogeny thus resembles that of S. murrayii, but only a small amount of mazaedial material is deposited on the spore surface. The classification of the species is discussed and it is concluded that the genus Sphaerophorus as presently circumscribed is very heterogeneous.