<i>Isoetes maxima</i>, a New Species from Brazil

Abstract

Isoetes maxima from eastern Brazil is described as a new species. This taxon differs from other fully aquatic species in South America by a combination of its overall size, leaf coloration, finely tapering subulae, and megaspore morphology. While examining Isoetes from eastern Brazil, we encountered a specimen whose large size and dark coloration are unlike any known species from that region. The plants have numerous, very narrow, densely packed, and finely tapering leaves, and its megaspores are rugulate to tuberculate. In contrast, other large Isoetes in this region of South America have broader leaves that are less densely packed, and reticulate megaspores (Fuchs-Eckert, 1986; Macluf et al., 2008). The specimens in question were collected by Aloysio Sehnem in 1970. Sehnem determined his collection to be a new species and designated it so on the label as Isoetes maxima. The label indicates the collection as the intended holotype; however, Sehnem never described or validly published the new species. We have elected to use the name that Sehnem had inscribed on the specimen label since the overall stature and robust appearance of the taxon merit the appellation.