Leaf anatomy of the genus Ehrharta (Poaceae) in southern Africa: the Villosa group

The leaf blade anatomy of Ehrharta villosa Schult. f. var. villosa, var. maxima Stapf and E. thunbergii Gibbs Russell is described and illustrated. These three taxa, constituting the Villosa species group, share a diagnostic leaf anatomy distinguished by the absence of a distinct midrib, adaxial semi-radiate mesophyll with the abaxial chloren- chyma palisade-like in arrangement, rectangular long cells and the stomatal apertures which are overlapped by four cuticular flanges projecting from the two adjacent interstomatal cells. These combined attributes characterize this species group, and the stomatal flanges are unique to this group in the genus Ehrharta Thunb. Microhairs are absent in E. villosa but are present in E. thunbergii which also possesses abaxial prickles and plentiful, rounded silica bodies not associated with cork cells as in E. villosa. These two taxa can. therefore, be separated anatomically. Nevertheless, they share many features and are undoubtedly closely related and their classification in the same species group is substantiated by the anatomical evidence presented in this paper.