Leaf Anatomical Studies of Alchornea Sw., Mallotus Lour. and Macaranga Thou. (Euphorbiaceae) from Some Parts of Nigeria

Background and Objective: The members of the genera Alchornea, Mallotus and Macaranga from Euphorbiaceae are closely related and difficult to differentiate.The leaf anatomy of these genera was studied to determine the interspecific and inter-generic variation among these taxa.Materials and Methods: Epidermal peels of the leaves were made with forceps.The petiole and midribs were fixed in FAA, dehydrated, sectioned, stained, observed and photo-micrographs taken with a trinocular research microscope (Amscope T340B) fitted with Amscope digital camera.Results: These genera share some similar characteristics such as paracytic stomata, trichome types, vascular bundle type and arrangement, petiole and midrib outlines, layers of palisade and spongy mesophylls, crystal (druses) distribution, etc., in common.Although some of these characteristics overlap among these taxa some of them such as trichome type, stomata type and distribution, crystal (druses) distribution, midrib and petiole vascular bundle pattern, etc., could be diagnostic at species and generic levels.We observed the peltate glandular hairs only on the adaxial surface of Mallotus oppositifolius and Mallotus subulatus but not in the other genera (Alchornea and Macaranga) studied.This character made this genus distinct from Alchornea and Macaranga. Conclusion:Trichome types, stomata types, petiole and midrib vascular bundle patterns and crystal (druses) distribution were diagnostic at species and generic levels and could be used to differentiate these taxa.