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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.
 

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Nutlets of 20 taxa of the tribe Marrubieae were examined by scanning electron microscopy (SEM) and detailed descriptions of nutlet micromorphological features for all examined taxa are provided. The nutlets exhibited variation in size, shape, color and surface sculpturing. The nutlets shape of most species studied is ovate, but rounded, broad ovate, elliptic, lanceolate, triangular and oblong can also be found in a few species. Six basic types of the sculpturing pattern of nutlet surface can be distinguished: reticulate, foveolate, scalariform, ruminate, pusticulate and colliculate-granulate. The most common type of nutlet sculpturing among the studied species is reticulate, but the variation in size and shape of their composing cells provided useful diagnostic characters. Our investigation revealed that the type of sculpturing was more useful in taxon delimitation among Marrubium species and allies at the species rank.