In order to find additional diagnostic features, the anatomical structure of petioles of eight species of Spirae in the flora of Ukraine was studied. It was established that the following anatomical features are significant diagnostic characters: shape of petiole cross-section; presence, location and shape of trichoma; cuticle thickness on the outer cell wall of petiole epidermis; pecularities of the structure of vascular system; number of inclusions of calcium oxalate around the main vascular bundle. It was shown that morphologically well-defined species, S. hypericifolia, S. crenata, and S. chamaedryfolia, essentially differ in anatomical features of petiole structure. A presence of significant distinctions in the structure of petioles of the related species S. media and S. polonica is an additional argument for taxonomic separation of the latter one, whereas the absence of such features in morphologically close species S. ulmifolia and S. chamaedryfolia may be an additional confirmation of the uncertain status of S. ulmifolia.
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