| Resumo: |
Ridley (1883) based the genus Acriulus (Cyperaceae) on two species, A. madagascariensis Ridl. from Madagascar, and A. griegifolius Ridl. from Angola, the former of which must be considered the nomenclatural type, as the generic characters were chiefly taken from it, and the latter species was but inadequately known at the time. The author originally admitted a close affinity of Acriulus to Scleria, but “the different habit, the solitary spikeiets, and the deeply cleft style not continuous with the ovary” he regarded as sufficient to base a new genus upon, and, later on even as so important that he placed Acriulus in a different tribe, viz in Cryptangieae, not in Sclerieae (Ridley, 1884). Having had the opportunity to study a fairly great number of Acriulus specimens, I am now convinced that neither the so-called generic characters mentioned by Ridley nor any other feature justify their exclusion from Scleria. The distinct articulation between style and ovary occurring in several cyperaceous genera, such as Fimbristylis, Bulbostylis, Eleocharis, and Rhynchospora, undoubtedly furnishes a first-class character for generic delimitation. However, in Acriulus there is no question of the style being articulated with the ovary in this way, nor could I find any structural difference with the gynoecium in Scleria (fig. c and d). Deeply cleft styles are common in Scleria. There can hardly if at all be question of a habit peculiar to Scleria, a very large genus comprising annuals as well as perennials, both groups with numerous species of very diversified stature ranging from dwarfy to very stout. Therefore the alleged peculiar habit of Acriulus cannot be taken into account at the generic level. Besides, in Scleria poaeformis Retz., which may be the nearest ally of Acriulus, the numerous male spikelets are solitary, about evenly distributed along the branches of the panicle, and the few nut-bearing spikelets mostly restricted to the base of those branches, just like in Acriulus.
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