Leaf anatomy of the genus <i>Ehrharta</i> (Poaceae) in southern Africa: the Villosa group

Abstract

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 anatom­ ically. 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. UITI'REKSEL Die blaarskyfanatomie van Ehrharta villosa Schult. f. var. villosa en var. maxima Stapf en E. thunbergii Gibbs Russell word beskryf en geillustreer. Hierdie drie taksons, wat die Villosa-spesiegroep verteenwoordig, vertoon n diagnostiese blaaranatomie. gekcnmerk deur die afwesigheid van n duidelike hoofaar. semi-radiale adaksiale mesofil met die abaksiale chlorenchiem palisade-agtig gerangskik, reghoekige langselle en die huidmondjie-ope-ninge wat oorvleuel word deur vier kutikulêre krae wat vanaf die twee aangrensende selle strek. Die kombinasie van kenmerke onderskei hierdie spesiegroep. en die huidmondjie-krae is uniek by hierdie groep in die genus Ehrharta Thunb. Mikrohare is afwesig by E. villosa maar aanwesig by E. thunbergii wat ook abaksiale stekelhare en volop ronde silikaliggaampies, wat nie met kurkselle geassosieer is soos by E. villosa nie, besit. Hierdie twee taksons kan dus anatomies onderskei word maar het nietemin baie kenmerke gemeen en is ongetwyfeld nouver-want aan mekaar en hul klassifikasie in dieselfde spesiegroep word ondersteun deur anatomiese gegewens wat hier aangebied word. identified as E. villosa and 10 as E. thunbergii (= E. gigantea) but considered as a single species. This paper describes and illustrates the leaf blade anatom y of the taxa of the Villosa group and dis­ cusses the affinities of these taxa and of the species group by reference to this anatomical evidence. By im plication the anatom ical data is com pared and contrasted with the morphological data as it is reflec­ ted in the classification of the group (Gibbs Russell 1987). The herbarium voucher specimens used in this anatom ical study were included in the sample on which the above taxonom ic conclusions were based.

Biology and control of pypgrass

“…Microscopic examinations of Turakina Beach specimens of pypgrass by Hodder (1997) have confirmed that plants are the same as those described by Ellis (1987). Pypgrass is a C3 plant, so does not have the physiological advantages of C4 plants with respect to efficient use of water.…”

Taxonomy of the genus <i>Ehrharta</i> (Poaceae) in southern Africa: the Villosa group

“…E. villosa var. villosa, which is concentrated geographically in the middle part of the distribution of the group, also has morphological and anatomical (Ellis 1987b) interm ediates to both the other taxa. The rhizome differences between the species may be related to habitat differences.…”

“…Morphologically, the Villosa group is linked to the Calycina group by the hairy spikelets with long glumes, and to the C a pensis group by the large spikelets with short-awned or m ucronate and stipitate sterile lemmas, and by the 'bulbous' internodes. Ellis (1987b) identified as E. villosa and 10 as E. thunbergii ( = E. gigantea) but considered as a single species. This paper describes and illustrates the leaf blade anatom y of the taxa of the Villosa group and dis cusses the affinities of these taxa and of the species group by reference to this anatomical evidence.…”

“…Besides these characters of habit and spikelet, the two species share features in leaf anatom y (Ellis 1987b). Within the group, the species differ mainly in spikelet size, relative glume length, rhizome structure, and in habitat and distribution, as well as in anatomical characters (Ellis 1987b). All the taxa are robust and have long, stout rhizomes.…”

“…The Villosa group is distinguished m orpholo gically by large spikelets 10-18 mm long that have sterile lemmas with conspicuously bearded bases, profusely hairy sides and m ucronate to aristate tips; and by a suffrutescent habit with culms woody at the base and with reduced leaf blades. Besides these characters of habit and spikelet, the two species share features in leaf anatom y (Ellis 1987b). Within the group, the species differ mainly in spikelet size, relative glume length, rhizome structure, and in habitat and distribution, as well as in anatomical characters (Ellis 1987b).…”