According to the data in Mala flora Slovenije (Wraber, 2007) four species of the genus Diplotaxis named D. muralis, D. tenuifolia, D. erucoides and D. viminea grow in Slovenia. The determination of the specimen is often difficult due to the lack of reliable determination characters. I have gathered the discriminative characters from floras and determination keys from neighbouring countries and checked them on the herbarium material from Herbarium LJU. I have examined 53 herbarium sheets, two of them were D. erucoides, 25 D. muralis and 25 D. tenuifolia. 9,5 % of plants, previously identified as D. muralis, were in fact D. tenuifolia, and 15 % of plants, previously identified as D. tenuifolia proved to be D. muralis. Both of D. erucoides sheets were correctly identified. D. viminea is not represented in the herbarium collection. I have measured 9 morphological characters in 50 plants of the herbarium material of D. muralis and D. tenuifolia. Based on the results, I have created an identification key, for the species that thrive in Slovenia. D. viminea is differentiated from other species by the size of the petals which are smaller compared to other species, by having sterile outer stamens, and by a leafless stem. D. erucoides can be reliably recognized by the whitish thickenings on the tips of the teeth of leaf margin. Reliable discriminative characters for D. muralis and D. tenuifolia are also: the presence or the length of the carpophore, which is longer on the species D. tenuifolia, the length of the anthers, which are longer on D. tenuifolia and the length of the petals and sepals, which are also longer on D. tenuifolia. Based on the data from the herbarium labels a distribution map of Diplotaxis species in Slovenia was made. D. tenuifolia and D. muralis grow in most parts of the country but there are no herbarium data for the north-easternmost and southeast part. D. erucoides was found in the area of the city of Ljubljana almost 100 years ago and was never observed afterwards. To get the representative distribution map of the species, additional field data should be collected.
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