Viola section Melanium (Violaceae) in Italy. New data on morphology of Viola tricolor-Group

摘要

Italian species of the Viola tricolor group, Sect. Melanium are examined from the morphological view-point. Additional diagnostic characters have been highlighted on the basis of in situ and ex situ experimental data, direct analysis of exsiccata andhigh resolution digital images of several Herbaria, check of previous international literature. Measures have been taken on well developed flowers after a given vegetative period. Diagnostic features of stigma, label-lum, position of opening to the stigmatic chamber and detailed photos are provided. Scanned images of stipules and corresponding leaves taken from the lower, median and upper part of the stem are also provided. These images provide clearer discrimination and correct identification of this difficult group. A synoptic table with the essential features of V. kitaibeliana, V. hymettia, V. parvula, V. arvensis subsp. arvensis and V. tricolor subsp. tricolor has been framed. Exsiccata are checked whilst some of them are revised. Therefore the Italian distribution area has been updated. The occurrence of V. hymettia has been verified in the Tyrrhenian Antiapennine sector (Lazio), where it is widespread mainly in the Viterbo environments, and in the Murge tarantine (Puglia). Extreme morphologicalvariants of V. arvensis / V. tricolor and apparent hybrids between them have been reported for Central Italy, giving evidence of the great variability of the group. Up to now the occurrence of V. arvensis subsp. megalantha in our territory has not beenconfirmed.