The Leaf Anatomy of Leptospermum Forst. (Myrtaceae)

Abstract

The leaf anatomy of 40 species of Leptospermum Forst. (Myrtaceae) is described in detail. The genus shows a fairly constant, typically myrtaceous leaf structure with isobilateral mesophyll and the presence of schizogenous oil cavities as constant characters. Variation occurs in stomatal type, sculpturing of the cuticle, persistence of the indumentum, and structure of the oil cavities. Both perigenous and mesoperigenous types of stomatal development have been observed. A number of characters show a considerable variation below the species level. The pattern of anatomical variation does not support Bentham's subdivision of the genus into three sections. Alternative subdivisions cannot be proposed on account of considerable overlap of the character complexes of the individual species. In some cases it is, however, possible to suggest mutual affinity (e. g. between L. laevigatum and L. coriaceum) on the basis of leaf anatomy. A comparison of the available ecological data with anatomical characters supports some of the generalized trends for increased xeromorphy with water availability. On the whole, however, all species of Leptospermum, including the mesic ones, show a rather xeromorphic leaf anatomy.