Anatomy and Systematics in the Costus afer - C. lucanusianus Complex (Costaceae)

Abstract

The anatomy of lamina, rhizome and root of three taxa of Costus was investigated with a view of establishing interrelationships among the previously confused species of the genus. Differences in features of the vegetative anatomy suggest that a separate specific status for C. afer and C. lucanusianus is justified as opposed to the conspecific treatment given to them by previous researchers. A hybrid collection of these Costus species does not merit a separate specific status, although it possessed distinct anatomical features. The systematic importance of this investigation is clear since a 3-4 layered spongy mesophyll of C. afer is different from a 4-5 layered spongy mesophyll of C. lucanusian~ and the 2-3 layers of the putative hybrid. Similarly the hexarch, nonarch and polyarch vascular bundle of the root of C. afer, C. lucanusianus and the Costus hybrid respectively, are all distinguishable attributes of these taxa that are important in systematics.