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

crispatissimum usually have curved walls, while cell walls in D. flexicaule are usually straight or only slightly curved. Basal juxtacostal cells in D. crispatissimum are usually narrowly elongate and distinctly porose, at least in some leaves (several leaves have to be studied!), whereas in D. flexicaule the cells are slightly shorter and usually eporose, sometimes indistinctly porose. This and the preceding character are stressed by Fris voll of being of particular importance in naming plants. Marginal cells form some kind of hyaline border around the middle of the sheathing leaf part in both taxa, but these cells are longer, more thin-walled in D. crispatissimum, the border is (1)2—4 cell rows broad and indistinctly delimited towards the inner cells, whereas in D. flexicaule cells are shorter, have thicker walls, and the border is (0)1-2(3) rows broad and usually distinctly marked towards the inner cells. Considerable difficulty was encountered with the observation of dorsal costa cells in relation to adjacent lamina cells. A detailed investigation of some typical specimens of both taxa revealed that two additional circumstances have to be taken into account: (i) Length of costa cells as well as that of lamina cells varies in a gradient from leaf base to apex. Dorsal costa cells are longest at the leaf base, becoming progressively shorter towards the upper end of the sheathing leaf base, then remain constant or slightly increase in length towards the apex. Lamina cells show a similar trend, but to a different extent, depending on the species and also on habitat conditions; dry-growing ecads having shorter cells. (ii) Dorsal costa cells are not homogeneous, but rows of shorter cells often alternate with rows of longer cells, these rows sometimes extending over a few cells only. This feature is evident in Frisvoll's illustrations (Figs 1 and especially 15), but its relevance is not considered by that author. When comparing the length of dorsal costa cells and lamina cells, it must therefore be specified (i) which part of the leaf is examined and (ii) if short or long costa cells (or average values) are considered. In the author's experience, a comparison of dorsal costa cells and adjacent lamina cells should be made at or slightly above the middle of the sheathing part of the leaf. At this point of the cell length gradients, in D. crispatissimum lamina cells are still rather long and costa cells have already shortened to the extent that longer lamina cells are adjacent to short costa cells (Fig. 15 in FRISVOLL 1985), whereas in D. flexicaule lamina cells are in general shorter and dorsal costa cells longer, so that anywhere from leaf base to apex lamina cells will be found to be shorter than costa cells.