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SummaryItalian species of the Viola tricolorgroup, Sect. Melaniumare examined from the morphological view-point. Additional diagnostic characters have been highlighted on the basis of in situand ex situexperimental data, direct analysis of exsiccataand high 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, labellum, 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. arvensissubsp. arvensisand V. tricolorsubsp. tricolorhas been framed. Exsiccataare checked whilst some of them are revised. Therefore the Italian distribution area has been updated. The occurrence of V. hymettiahas been verified in the Tyrrhenian Antiapennine sector (Lazio), where it is widespread mainly in the Viterbo environments, and in the Murge tarantine (Puglia). Extreme morphological variants of V. arvensis/V. tricolorand 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. arvensissubsp. megalanthain our territory has not been confirmed.

RiassuntoVengono illustrati i risultati dell'indagine che ha preso in esame tutti i dati floristici raccolti negli anni 1991–1996 nel territorio della Riserva Naturale Monte Rufeno, sita nel comune di Acquapendente (VT), i dati della letteratura e i saggi d'erbario conservati principalmente in UTV. Dopo una breve descrizione dei lineamenti fisici, climatici e vegetazionali del territorio si riporta l'elenco della flora vascolare, corredato di note esplicative per le entità di particolare interesse per rarità e altro. Le piante spontanee o spontaneizzate sono 1050 mentre le introdotte in tempi recenti sono 20, per lo più legate ai casali, ormai da tempo abbandonati, e alle opere di rimboschimento che hanno interessato l'area fino alla fine degli anni '60. La flora spontanea e spontaneizzata è ripartita in 456 generi e 100 famiglie: Legutninosae, Compositaee Gramineaehanno più di 100 entità. 36 specie sono incluse nella Lista Rossa Regionale delle Piante d'Italia; di queste Vicia laetaCesati e Hottonia palustrisL. sono vulnerabili (VU) in Italia, mentre Santolina etruscaMarchi et D'Amato è ritenuta a minor rischio (LR). Taraxacum palustre(Lyons) Symons risultava estinto in natura (EW) nel Lazio mentre Callitriche bruttaPetagna, V. laetaCesati e H. palustrisL. gravemente minacciate (CR). 88 entità sono ritenute rare o rarissime per la regione, alcune hanno a M. Rufeno l'unica stazione ad oggi nota o risultano nuove per la flora laziale. Attraverso un confronto con flore già edite per aree limitrofe, viene evidenziata la valenza floristica del territorio, legata fra l'altro alla posizione geografica “marginale”, alla presenza del F. Paglia e alla grande varietà di tipologie vegetazionali concentrate in una superficie assai ridotta. Dagli spettri biologico e corologico risulta una collocazione nella Regione temperata con moderata influenza mediterranea in accordo con l'ubicazione e i tipi di vegetazione presenti.

The use of life-forms in phytosociological classifications: an example with data from xerophilous pastures.—The classification power of life-forms connecting to phytosociological data processing for xerophilous pastures of Central Southern Apennine (ecological classification) is discussed. Saturejo montanae-Brometum erecti Avena, Blasi 1979 and Seslerio nitidae-Brometum Bruno 1968 are compared on the basis of their weighted life-forms spectra. The high correlation between classification obtained by floristic data and classifications by life-forms is stressed.

A method to quantify the dynamic schemes of vegetation based on information functions.—The dynamic schemes of vegetation as proposed by Braun-Blanquet have been never quantified with the aim to give indirect measures of the probability of transition between the types. This work presents a method that quantifies the arrows between the types by means of a redundancy measure. This is calculated by comparing the phytosociological types two by two. Redundancy, as proposed here, measures the similarity between the tables not only based on species composition but also on the basis of species cooccurrence. The method relies on the assumption that in a succession the higher is the redundancy between the types, that are presumably in sequence, the higher is the probability and then the velocity of transition from one type to another one. An example is given with data from coastal dune grasslands of the Venice Lagoon.

The method known as Analysis of Concentration (AOC) is proposed as a tool to measure the predictivity of binary data for cover data. The application of AOC to structured tables of oak forests of Central Italy has proved that binary data are more predictive for cover than cover for binary data. The ordinations produced by AOC with binary and cover data are very similar and interpretable with similar results.