The genus of forget-me-nots (Myosotis) belongs to the family of borages (Boraginaceae). The genus includes approximately 100 different species. Most of these can be found in temperate climate; however some species also grow in the mountainous parts of the tropics. For the purpose of this master's thesis, I studied the group of Field forget-me-nots in Slovenia in detail. The group consists of three forget-me-not species (M. arvensis (L.) Hill, M. ramosissima Rochel in Schultes and M. stricta Link ex Roemer & Schultes). The two most important goals of the research were to find key morphological characteristics to distinguish the species from the Field forget-me-not group between one another, and to determine where in Slovenia these species grow. In our research we used the herbarium specimens from the herbarium of University of Ljubljana (LJU) which were previously identified as one of the Field forget-me-not species. The data from herbarium labels were collected in a table to which we also added some other information that helped us with the selection of an appropriate sample for our measurements. We defined 17 different morphological characteristics in the selected sample (14 numerical and 4 descriptive), most of which can also be found in relevant literature. We established that the most important distinguishing features between the species are the characteristics of the nutlet, the pedicels of calyxes with already developed nutlets, and the calyx. The distinguishing features of nutlets that have proved useful are: length and width of the nutlet, width and height of the attachment area, position of the attachment area, length from the nutlet base to its widest part, the shape and symmetry of the nutlet, presence of the rim (edge) on the nutlet, and, though only conditionally, also the colour of the nutlet. We found out that also the length of the pedicel of the calyx with developed nutlets and its growing angle between the pedicel of the calyx and the stem are two other valuable distinguishing features. Two distinguishing characteristics of the calyx during the fruiting period are the shape of calyx lobes, and the openness and closing of the calyx. However, the measured features of the flowers did not prove to be among the most suitable ones for species identification – the only distinguishing feature that proved appropriate was the measurement of the width of the corolla. After the completion of the measurements and data processing we created a dichotomous key for species identification. In the end we also revised the rest of the herbarium material and created new maps of species distribution in Slovenia using the herbarium specimens from the herbarium LJU. We confirmed that all three species of Filed forget-me-nots were present in Slovenia. The most widespread species is M. arvensis (L.) Hill, whereas the rarest (with only one specimen in the herbarium LJU) is M. stricta Link ex Roemer & Schultes.
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