LIMITED TAXONOMIC VALUE OF PALEA INTERCOSTAL CHARACTERISTICS IN NORTH-AMERICAN FESTUCA (POACEAE)

Morphology of the intercostal palea region of 34 Festuca species found in North America was investigated using scanning electron microscopy. Palea epidermal features are most diverse in the palea apical region and fully developed in florets approaching anthesis. The intercostal r egion has long cells 3-15 times longer than wide, with walls that vary from slightly to prominently thickened, and from almost straight to s trongly undulate. This variation was observed among paleas collected f rom different locations and sometimes even on a single palea. The dist ribution of short cells, almost square in outline, among the long cell s varied with species from solitary to paired and from abundant to spa rse. Four forms of trichomes were recorded: papillae, hook trichomes, prickle hairs, and macrohairs, with one form usually predominating per species. Silicon was detected in some short cells and commonly in the tips of trichomes. A key to species groups is presented.