Zs. P. Komáromy szerk.: Studia Botanica Hungarica 12. 1977 (Budapest, 1977)
Radics, Ferenc: The identification of Rorippa species and hybrids (Cruciferae) based on external morphological features of their seeds
cies: Rorippa repens BORB. (R.' amphibia x silvestris) (Plate III, 1); Rorippa hungarica BORB. (R. amphibia x austriaca) (Plate III, 4); and Rorippa erythrocaulis BORB. (R.. amphibia x palustris) (Plate III, 2). As the seed picture of Rorippa repens shows, in the combination of species the features of R. austriaca-type are not present, it is the character of R_. silvestris which prevails: its shape rather widened below, the hilum region is not arched but rather obtuse, and on the margin there is a darker stripe; on the seed picture of R. hungarica the morphological features of seeds of R, silvestris are not present; finally, as to the seeds of R_. erythrocaulis , the features of R. palustris are combined, these latter features cannot be observed on the seeds of R. barbaraeoides (I mentioned only the morphological features visible on the photos. ) Rorippa armoracioides TAUSCH (sub Nasturtio 1840) Syn. : R. x armoracioides (TAUSCH 1840 sub Nasturtio) FUSS 1866. This taxon is mostly considered to be a hybrid of R. austriaca and R,, silvestris . However, neither BORBAS (1879a), nor FRÖHLICH (1914) has unequivocally affirmed this, whilst POLAK (1880) was inclined to take it for a hybrid of R. austriaca and R. palustris . FRÖHLICH said only that it is "probably" a hybrid of R. austriaca and R. silvestris . On the rather similar seeds of Rorippa armoracioides, the characteristic features of R. austriaca and R. silvestris can be observed, namely; the shape of seeds and that of the hilum region, the darker margin of seeds and the thorn-like projection of the thickened cell-walls on the margins (Plate III, 3). These features are still more explicit on the likewise similar seeds of Rorippa terrestris TAUSCH, also found in the Carpathian Basin (Plate III, 5). According to BORBAS (1897), these latter Rorippa plants, regarding their morphological features, are the hybrids of Rorippa austriaca and R. silvestris . On the other hand, on the seeds of the specimens of Rorippa armoracioides to be found in our collection also the features of Rorippa palustris (shape and seed surface) can be perceived in various combinations (Plate III, 3). Therefore also Rorippa armoracioides seems to be a stabilized hybridogenous species of triple hybrid origin in such a degree, that there is in our collection a tall Rorippa specimen (No. 70, 106), collected near Nagyenyed, Transylvania, together with R. armoracioides , in an abandoned ditch of the river Maros, but it has been determined as Nasturtium subarmoracioides (Nasturtium barbaraeoides x armoracioides) CSATÓ et SIMK. (Plate IV, 1). The seed picture represents the features of R. austriaca and R. silvestris more distinctly and visible, whilst the features of R. amphibia and R. palustris are shown in an entirely new combination. At the same time, it is characteristic both for the simple primary hybrids and for the mixture of hybridogenic species that their seeds are of various size and shape, and there are many sterile and even distorted seeds among them.
