Nutlet micromorphology and its systematic implications in Phlomoides Moench (Lamiaceae)

Nutlets of 20 taxa of Phlomoides, representing most of the currently recognized sections were examined by scanning electron microscopy. The basic shape of nutlets in most taxa studied is broadly ovate, but ovate, triangular and oblong ones can also be found in few species. Regarding the sculpturing pattern of nutlet surface, four basic types can be distinguished: reticulate, scalariform, ruminate and rugose. The reticulate type is the most common among the studied species, but the variation in alignment, size and shape of its composing cells provide further evidence that are useful as diagnostic characteristics. However, the type of sculpturing is more useful for separating species within the sections, rather than correlating them to each other. For example, sect. Filipendula show four different types of sculpturing. Therefore, nutlet microsculpturing is not useful in separating large natural groups like sections in this genus. It seems also that contrary to other genera of Lamiaceae, nutlet characters are of low phylogenetic value in this genus.