Two new species of Chusquea (Poaceae: Bambusoideae: Bambuseae) from Mexico, one of them morphologically unusual, and a key to the Mexican sections of Chusquea

Based on recent morphological work that included an extensive taxonomic investigation of herbarium specimens and fieldwork in the Mexican state of Michoacan, two new Chusquea species, C. matlatzinca and C. cortesii, are here described and illustrated. C. matlatzinca is a narrow endemic to Michoacan and has unusual vegetative morphology. Chusquea matlatzinca is compared with the rare, high elevation Mexican endemics C. perotensis and C. bilimekii, from which it can be separated by its thick-walled, hollow culms, extravaginal branching pattern and short inner ligule of the foliage leaves. Chusquea cortesii is compared with C. aperta and C. nelsonii, from which it can be separated by possessing wider and longer culms, fewer subsidiary branches per node, shorter nodal regions with a slightly more prominent supranodal ridge, slightly mottled internodes and longer and wider foliage leaf blades. Morphological keys to the sections of Chusquea present in Mexico and to the Mexican species of each of these two sections, including the new species, are presented.