Ascocarp Development in Lophodermium Pinastri

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Abstract
Ascocarps of Lophodermium pinastri develop in the spring on overwintered needles of Pinus banksiana. The ascocarp primordium consists of a hyphal network that extends between the leaf cuticle and hypodermis. In its growth, this mycelium dislodges certain epidermal cells that subsequently occupy a position at the base of the developing apothecium. The mycelium just under the cuticle becomes the carbonaceous clypeus while that directly above the hypodermis forms the hypothecium. The latter gives rise to paraphyses whose apices are free from the inner surface of the clypeus. There is no differentiated ascogonium, the asci arising from the paraphyses. An ascus can be produced directly from one of the basal cells of an individual paraphysis, or from a basal paraphysal cell which proliferates into a limited system of ascogenous elements. The sum total of many such systems, each ramifying for a short distance through the hypothecium, comprises the hymenium. The frequent occurrence of crozier formation is interpreted as indicating a dikaryotic condition, and it is suggested that initiation of the dikaryon may be associated with the points of anastomosis (hyphal bridges) between adjacent paraphysal cells.