Types of Leaf

Based on how deeply the lamina is incised, leaves are of two main types:

• Simple leaf — the lamina is entire, i.e. it is not divided all the way down to the midrib/rachis into separate leaflets.
• Compound leaf — the lamina is divided into a number of separate leaflets.

Compound leaves are themselves of two types:

a. Pinnately compound — the leaflets are arranged laterally along a common axis called the rachis, which represents the midrib of the leaf. Depending on how the rachis itself branches and how many leaflets are present, pinnately compound leaves are further described as unifoliate (one leaflet, e.g. Citrus), bifoliate (two leaflets, e.g. Bauhinia), trifoliate (three leaflets, e.g. Oxalis), quadrifoliate (four leaflets, e.g. Marsilea) or multifoliate (many leaflets, e.g. Bombax); and, by the pattern of division, as imparipinnate (ending in a single terminal leaflet, e.g. Rosa), paripinnate (ending in a pair of leaflets with no odd terminal one, e.g. Cassia), bipinnate (the rachis itself branches once more before bearing leaflets, e.g. Caesalpinia), tripinnate (a further order of branching, e.g. Moringa) or decompound (very …