Problems of distinction among succulent Euphorbia species from eastern tropical Africa

Problems of distinction among succulent Euphorbia species from eastern tropical Africa. Identification of herbarium specimens of succulent Euphorbia species is especially difficult due to distortion of important characters upon drying. Problems encountered in collecting and preserving material result in poor representation in the herbarium, and true variation and distribution of closely related taxa are thus often established only from field studies. These problems are exposed and some solutions given in four groups of species from east and northeast Africa: the non-spiny E. schimperi-nubica group, the single-spined E. triaculeata group, the shrubby E. heterochroma-stapfii group and the tree E. nyikae-kibwezensis group.