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

pearance of D. flexicaule, and lax, long forms of D. flexicaule exist (e.g. the Hungarian specimens from Sas-kő in Mátra Mts). Tomentum may be strong in D. crispatissimum and weak in D. flexicaule. In the original material studied by FRISVOLL (1985), stem length is (1-) 4-5 (-9) cm in D. crispatissimum and (1.5-) 4-5 (-7) cm in D. flexicaule, i.e. considerable overlap exists. Short-leaved flagelliferous shoots are absent from D. crispatissimum, but fragile branches with unmodified leaves occur. Orientation of dry leaves is a very characteristic feature of the taxa that is easily recognized even at low magnifications. In contrast with the meaning of the specific epithet "crispatissimum" the leaves of D. crispatissimum are rather straight, usually slightly or not at all flexuose (except in some sheltered habitats), often falcate; those of D. flexicaule are usually flexuose, rarely falcate. The long subulae of D. crispatissimum are, however, often spirally twisted together, which happens only rarely in D. flexicaule with its generally shorter subulae. Leaf length is related to robustness, thus leaves of D. crispatissimum are 4-5 (-7.2) mm long, while those of D. flexicaule are (1.4-) 3 (-4.6) mm long, but this character is very strongly dependent on growth conditions, dry-growing ecads having much shorter leaves in both taxa. In mixed stands, however, D. crispatissimum always has longer leaves than D. flexicaule. Leaf shape and subula length are interrelated. Leaves of D. crispatissimum are gradually narrowed from a convolute expanded part into a subula that makes up more than 2/3 of total leaf length, whereas in D. flexicaule the sheathing leaf base is rather suddenly contracted into a comparatively short subula. This character is not always easy to establish, because some leaves may appear intermediate. The upper limit of the sheathing leaf base may be difficult to assess in leaves that gradually taper towards the subula, in which case the relative length of the subula is hard to estimate. In contrast with D. flexicaule, in typical D. crispatissimum the leaf is not really sheathing the stem. The difference in leaf insertion is well illustrated in CASAS et al. (1990). It is important that vegetative leaves are examined, because perichaetial leaves have a different form (and also areolation). Dentation of the leaf apex is variable in both taxa and thus seems to be of less value in naming plants. Cells (in the middle) of the sheathing part of the leaf are variable in both taxa but usually shorter in D. flexicaule. Cell length is not constant within a leaf, but varies in a gradient, cells becoming shorter towards the apex. At the top of the sheathing part, lamina cells may be isodiametric in both taxa, therefore this character must be studied further down. Plants of both taxa growing in dry places have shorter lamina cells. Some cells of the upper part of the sheathing base in D.