Mesanthophora, a New Genus of Vernonieae (Asteraceae) from Paraguay

Abstract

The new genus Mesanthophora is from a limestone area of central Paraguay. It looks similar to Lepidaploa, but has decurrent auriculate-based leaves, pedunculate heads from the middle of inter- nodes, nearly equal numbers of involucral bracts and florets, and triporate, totally lophate, strongly columellate pollen lacking a perforated tectum. A Paraguayan specimen belonging to the Aster- aceous tribe Vernonieae that was sent by the Mis- souri Botanical Garden for identification has proven to represent a distinctive, previously undescribed genus. A superficial resemblance to Lepidaploa proves misleading. Both the genus and the species seem undescribed in spite of the many members of the Vernonieae that have previously been described from Paraguay by such authors as Chodat (1901- 1902). The type specimen of the new genus has a general habit of the common neotropical Vernonian genus Lepidaploa (Cass.) Cass. (Robinson, 1990), with series of heads among large foliose bracts along the branches of the inflorescence. However, initial ob- servation shows that each head is pedunculate, un- like the heads of Lepidaploa. The new genus also differs by the position of the pedunculate heads on the middle of the internodes rather than at the nodes. The supra-axillary position seems rigorously main- tained throughout the inflorescence and is a char- acteristic that distinguishes the plant from all other Vernonieae. In a final distinction, the leaf bases are sessile, decurrent for up to 5 mm, and are auriculate below the decurrency. The decurrency holds the basal auricles of the leaf at a downward angle com- pared to the rest of the leaf blade. Lepidaploa does not have sessile auriculate leaf bases. Other South