SUMMARY -The early phases of basidiospore-derived infection of Me/ampsora pulcherrima (Bub.) Maire on the leaves of Mercurialis annua L. were studied by light microscopy, SEM and TEM. The fine morphology of the basidiospore germling penetration and intraepidermal infection structures is discussed in comparison with that of other rusts recently described. The direct penetration through the epidermal cell wall, characteristic of the rust basidiospore-derived germlings, is confirmed. The absence of an extrahyphal matrix around the intraepidermal vesicle and the presence of a collar around the vesicle neck are pointed out.

Present knowledge of host range and distribution of Melampsora pinitorqua Rostr. in Italy is reported. Melampsora larici-tremulae, which occurs at high altitude in the Apennines and the Alps and infects only larch, can infect pine also in artificial conditions.

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The germination ability of teleutospores of Melampsora pinitorqua Rostr. overwintered in different situations and under different types of soil cover was studied. The germmation period is affected by local environmental conditions. The intensity of germination of teleutospores overwintered in the underbrush is much lower than that of teleutospores overwintered on uncovered soil.

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