Journal of the East Africa Natural History Society and National Museum

In recent years there has been an increasing interest in several aspects of plant biology in the alpine zone of Mount Kenya. To my knowledge, at least a dozen research projects were carried out between 1977 and 1984. Fortunately, the flora of the region has been the subject of a fine monograph by Hedberg (1957), and the currently available volumes of the Flora of Tropical East Africa (FTEA hereafter) contain a majority of the alpine species. Although reproductive individuals are generally more prevalent on the mountain throughout the year when compared to the drier lowlands, many species are only rarely found in the reproductive state (personal observations). As part of a comprehensive study of the vegetation of the upper Tel'eki Valley on Mount Kenya, we produced this key based on vegetative characters. It has since proven useful (in manuscript form) in studies by various other researchers. It is hoped that its publication will facilitate and encourage future biological research on Mount Kenya. A lower elevationallimit of 3500 meters was chosen to eliminate a number of forest species that occur sporadicaJ.ly above the timberline. Several species not listed by Hedberg are included. These represent either new records for Mount Kenya, such as Helictotrichon umbrosum and CysLOpterisdiaphana. or new altitudinal ranges discovered in our studies, such as Kniphojia thomsonii and Asp/enium E (Agnew 1974). A separate paper will document the distribution, frequency, and ecology of the approximately 70 species found in the upper Teleki Valley. As an additional aid to identification, three short reproductive keys for difficult groups are appended to the main vegetative key. The first of these covers three species of Helichrysum, the second covers herbs with opposite entire leaves, and the third covers the grasses. For three genera (Poa, Co/podium, and Cerastium) of two species each, no reliable vegetative distinguishing traits could be found. These genera are included in the reproductive keys. One other genus deserves special mention. Hedberg (1957) and Clayton (1970) distinguished Pentaschistis minor and P. bowssica by panicle shape. The former reportedly has a linear panicle, and the latter an open panicle. In addition, their altitudinal distributions on Mount Kenya were thought to be disjunct (Hedberg 1957). We have found that not only can Pentaschistis spp. be found at intermediate elevations, but that panicle shape in P. minor varies with plant age and air temperature (T.P.) Young, personal observations). In addition, Clayton (1970) reports the existence of intermediates between P. minor and P. borussica. We have found no consistent vegetative differences, and both key out here as P. minor.