Centropogon (Campanulaceae: Lobelioideae) includes 216 species distributed from Mexico and the Lesser Antilles to Bolivia and Brazil. The genus is characterized by solitary axillary flowers or racemose terminal inflorescences, entire corolla tube, occluded anther orifice, baccate fruit, and ellipsoidal seeds twice as long as broad or less. Five sections are currently recognized Centropogon, Siphocampyloides Benth., Wimmeriopsis McVaugh, Burmeisteroides Gleason, and Niveopsis Lammers. The sect. Siphocampyloides, comprising 98 species, is distinguished by the possession of branched (i.e., arbusculiform) trichomes. However, other characteristics, such as floral features, suggest this may not be the optimum classification. The species of subsect. Peruviani McVaugh resemble sect. Burmeisteroides in corolla morphology, while those of subsect. Brevilimbati McVaugh resemble sect. Wimmeriopsis. Furthermore, branched trichomes occur infrequently in three other genera: Neotropical Burmeistera and Siphocampylus and Hawaiian Cyanea. Examination of trichome morphology via scanning electron microscopy reveals considerable variation among numerous species. Some trichomes are stalked while others are sessile. Trichome branching patterns observed include dendritic, multangulate, furcate, anfractuose, and echinoid. Other variation includes distance between branches, total trichome length, and total coverage of indumentum over the surface of the leaf. Evaluation of the data suggests a correlation between trichome type and other characteristics (e.g., floral features) traditionally used in the classification of the genus. The specimens examined from subsect. Peruviani had anfractuose, echinoid, and multangulate-dendritic trichomes, while the specimens from subsect. Brevilimbati had only dendritic or multangulate trichomes. Such data suggests that the current classification is suboptimal, and that a new classification is needed that utilizes all shared characteristics.

Key words: Campanulaceae, Centropogon, Lobelioideae, morphology, systematics, trichomes