On the Delimitation of the Genus Gahnia (Cyperaceae)

Although the Hawaiian Morelotia gahniaeformis Gaudich. and the J\ew Zealand Lampocarya affinis Brongn. are extremely similar in habit and also agree in numerous details, they were maintained as distinct, though closely related species by most authors of the last century. To be sure, Kunth (1837) had only seen specimens of the Morelotia species, Steudel (1855, p. 164) suspected the two to be but varietally distinct, and Hooker (1867) combined them under the binomial Gahnia arenaria Hook. f. On the other hand, Boeckeler (1874, p. 351-352) drew up two accurate descriptions especially pointing out the distinct and specifically different characters of their fruit. Kunth referred the species to Lampocarya R. Brown; Steudel, Hooker, and Boeckeler, who did not recognize this genus of Brown, classified them in Gahnia J. R. & G. Forst. Unfortunately most subsequent authors did not follow Boeckeler, but shared Hooker’s opinion. Some twenty years ago two monographs on the genus Gahnia were published. Both Benl (1940, p. 165-169, f. 6) and Kükenthal (1943, p. 86) ignored Boeckeler’s clear exposition of the differentiating characters. Beni found only a negligible difference between the two in the length of the inflorescence, and in Kiikenthal’s opinion the New Zealand specimens do not differ from the Hawaiian ones except for their paler leaf-sheaths and slightly more ciliate glumes. Therefore both authors referred Morelotia gahniaeformis and Lampocarya affinis again to the synonymy of Gahnia gahniaeformis (Gaudich.) Heller.