B. Papp szerk.: Studia Botanica Hungarica 32. 2001 (Budapest, 2001)

Erzberger, Peter: Ditrichum crispatissimum (Muell. Hal.) Paris, a new species of the Hungarian bryoflora, and Ditrichum flexicaule (Schleich. ex Schwaegr.) Hampe in Hungary

a single, extremely variable and widespread taxon. They list D. crispatissimum as a synonym of D. gracile, a name antedating D. crispatissimum by 5 years, and thus D. gracile would appear as the correct name. But since the taxonomic relations are not yet clear, at present the name D. crispatissimum is preferred in this paper. A worldwide revision is obviously urgently needed. CRUM and ANDERSON (1981) claimed that all differences in size, appearance and microscopical detail within the D. flexicaule complex could be related to habitat conditions, especially shade and moisture. However, FRISVOLL (1985) observed mixed stands in which the taxa were distinct, as had already TUOMIKOSKI et al. (1973). FRISVOLL (1985) also enumerates some "mixed collections". The logic of this approach has been criticized by WYATT et al. (1982). These authors in particular reject the extension of the method from mixed stands to mixed gatherings in herbarium specimens. In the Hungarian material of the D. flexicaule complex, two "mixed collections" were found, as described above: the single specimen from Koloska rocks containing D. crispatissimum together with D. flexicaule, and a specimen from Nagy István erőse, containing two forms of D. flexicaule differing in appearance and some microscopical details. In both cases, however, judging from the occurrence of companion species in the colonies, these mixed collections probably did not form part of mixed stands. Therefore, no taxonomic conclusions can be drawn from their observation. DULL and MEINUNGER (1989) recognize two varieties in D. flexicaule s. 1.: var. flexicaule and var. longifolium (Zett.) Hag., a synonym of D. crispatissimum according to FRISVOLL (1985). The distinction of the taxa in question at the varietal level seems more appropriate if the existence of intermediates can be demonstrated on a larger scale. The existing reports of intermediates in the literature are considered here to be of a preliminary nature, mostly for methodological shortcomings, as discussed above. Whether the Hungarian problematic plants described in this paper are only exceptions, as Frisvoll conceives specimens which are hard to name ("aberrant plants or difficult modifications from unusual habitats"; FRISVOLL 1985), or if they represent intermediates that frequently and as a rule occur together with more typical morphs of D. crispatissimum and D. flexicaule, remains to be resolved by further studies. * * * Acknowledgements - I am grateful to the curator of BP, Dr B. Papp, for the loan of specimens and for participating in the search for D. crispatissimum at Koloska rocks, to the curator of B for the permission to study some specimens, to C. Casas for examining the Hungarian specimen of D. crispatissimum, to Gy. Szél for help with preparing the map and to C. Kraft for linguistic corrections.