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In Europe, the genus Tolypella (Characeae) comprises four to eight Tolypella taxa in sections Rothia and Tolypella that have been distinguished by vegetative morphology and gametangial characters such as antheridial size and oospore wall ornamentation. However, morphological differentiation is difficult in some cases due to overlapping and variable vegetative features, which in many cases are difficult to observe clearly. To clarify the taxonomic status of the five European taxa of Tolypella in section Tolypella, sequence data of the plastid genes atpB, rbcL and psbC for Tolypella glomerata (Desv.) Leonh., Tolypella hispanica Allen, Tolypella nidifica (O.F. Müll.) A. Braun, Tolypella normaniana (Nordst.) Nordst. and Tolypella salina Cor. were combined with data on oospore morphology, including oospore wall ornamentation. Gene sequence data identified five distinct clusters, but they were not consistent with the morphologically identified five taxa. T. glomerata consisted of some of the samples morphologically identified as T. glomerata and seven samples of T. normaniana, while the remaining T. glomerata samples clustered with specimens of unclear affiliation (Tolypella sp.). We identified two clusters of T. hispanica within the European material: cluster T. hispanica I consisted of samples from various locations, whereas the second cluster (T. hispanica II) consisted of samples of T. hispanica from Sardinia Island. The remaining cluster consisted of all the specimens that had been determined as T. salina or T. nidifica in addition to two specimens of T. normaniana. Oospore morphology was most clearly distinguishable for T. glomerata. Oospore characteristics for all other taxa were not as informative but showed some geographical and/or environmentally influenced differences, especially for T. nidifica and T. salina. Our results suggest the need to further check the different taxonomy of Tolypella sect. Tolypella in which specimens normally identified as T. glomerata might be two different taxa, T. glomerata and an unidentified taxon; T. nidifica and T. salina are not separate taxa; T. normaniana is a diminutive variant of two different Tolypella taxa; and T. hispanica comprises two different taxa, one from the Mediterranean island Sardinia. [ABSTRACT FROM AUTHOR]

Aims: The objective of our study was to detect spatial patterns in the relationship of plant communities and rare species of wet field depressions to environmental factors such as climate, the size or geographic position of the field depressions and the soil properties. Location: Fifteen temporarily flooded field depressions along a 150 km long gradient from Brandenburg (NE Germany) to West Pomerania (NW Poland). Methods: To identify factors which define the occurrence of rare species, the vegetation of depressions with and without documented occurrence of Elatine alsinastrum were pairwise compared in 10 m × 10 m sampling plots. As the field emergence of the rare wetland plants was severely restricted by low precipitation during the study period, we performed a soil seed bank analysis instead of field sampling. Results: Our study sites were placed along a gradient of decreasing precipitation from the westernmost sites in Brandenburg to West Pomerania in the east. With decreasing precipitation we also observed an increase in the number and area of water bodies surrounding the study plots. Increased concentrations of P in soil, the occurrence of typical arable weeds as "indicator species" in the west and more perennial plants in the east suggest more intensive cultivation of the westernmost field depressions. Small water bodies harbouring higher numbers of species may be the result of greater smallscale habitat variation within our 100 m² sampling plots. Records of E. alsinastrum at both sites with and without former proof do not allow for clear conclusions on the impact of environmental factors on the occurrence of such rare species. Conclusions: Finds of 12 Red List species and four near-threatened species together with former records of several very rare charophytes verify the high nature conservation value of the study sites. As ongoing intensification of arable cultivation and drainage may seriously impact rare wetland plants, conservation measures should be taken to maintain their reproduction and to prevent future decline of their seed reservoir. [ABSTRACT FROM AUTHOR]

The correct name of the species of Nitella known as the "Least Stonewort" has long been under debate. The problem has now been resolved as Nitella confervacea (Brébisson) A. Braun ex Leonhardi. This taxon, once thought to be an endemic of northwestern France, was neglected for a long time. The basionym Nitella gracilis var. confervacea Brébisson and other taxa connected to this name are typified, and their taxonomic status is assessed. [ABSTRACT FROM AUTHOR]

Morphological features of oospores of Chara baueri A. Braun, one of the rarest charophyte species worldwide, were studied based on 100 oospores collected from a small and temporarily dried mid-field pond near Cedynia, Western Poland. This is the first Polish and fifth presently known locality of this species. For comparison 67 oospores from a German population (similar pond localized near Batzlow, Germany) were also measured. So far, data on morphology of C. baueri oospores as well as the species ecology are limited. The only more detailed study of oospores for this species was earlier performed on 15 oospores from Kazakhstan. Largest polar axis (LPA, length), largest equatorial diameter (LED, width), isopolarity index (ISI = LPA/LED x 100), number of ridges, width of fossa, distance from apical pole to LED (AND) and anisipolarity index (ANI = AND/LPA x 100) were measured. The comparative analysis revealed that the oospores from Poland are generally bigger and more prolate than the German ones. The differences for most of studied parameters were statistically significant. The finding is discussed in the context of habitat differentiation of both studied sites. Moreover, the results obtained of oospore measurements for both populations differs from most of the data known so far from the literature. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we discuss the Weyl matrix balls corresponding to an interpolation problem for J-Potapov functions in the open unit disk , which was studied in . In particular, we derive explicit expressions for the parameters of the Weyl matrix balls in terms of the given data. Furthermore, we examine the monotonicity of the sequences of the Weyl semi-radii. Finally, we discuss central J-Potapov functions, using their associated Weyl matrix balls. [Copyright &y& Elsevier]

Abstract: In this paper we discuss Weyl matrix balls in the context of the matricial versions of the classical interpolation problems named after Carathéodory and Schur. Our particular focus will be on studying the monotonicity of suitably normalized semi-radii of the corresponding Weyl matrix balls. We, furthermore, devote a fair bit of attention to characterizing the case in which equality holds for particular matricial inequalities. Solving these problems will provide us with a new perspective on the role of the central functions for the classes of Carathéodory and Schur. [Copyright &y& Elsevier]