What is a stipule?

$A$ unipinnate compound leaf can be differentiated from a branch having simple leaves by

Leaves arise from which part of the plant?

Swollen spongy petiole is present in

In $Acacia$ species,the first few leaves are pinnately compound. Then there are leaves with flattened petiole and fewer pinnae. The leaves of the adult plant have parallel-veined flattened petioles and no pinnae. It shows that:

In the leaf,vascular bundles are found in the