BATTERMAN, MCLYNDA R.W. and THOMAS G. LAMMERS.* Department of Biology and Microbiology, University of Wisconsin Oshkosh, Oshkosh, WI 54901. - Trichome morphology and its systematic implications in Centropogon and other genera of Lobelioideae (Campanulaceae).
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 section
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 subsection
Peruviani McVaugh resemble section Burmeisteroides in
corolla morphology, while those of subsection Brevilimbati
McVaugh resemble section 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, stalked-multangulate,
and dendritic-echinoid. Other variation that is observable includes
distance between branches, total trichome length, and total coverage
of indumentum over the surface of the leaf. Preliminary evaluation of
the data suggests some correlation between trichome type and other
characteristics (e.g., floral features) traditionally used in the
classification of the genus.
Key words: Campanulaceae, Centropogon, Lobelioideae, trichomes