Zygomorphic flower with vexillary aestivation, diadelphous androecium and marginal placentation occurs in
Pisum
Pisum commonly known as a pea is a genus of flowering plant belonging to family Fabaceae. In Fabaceae, the flowers are zygomorphic (bilateral symmetry), bisexual. The petals 5, polypetalous, the posterior outermost petal is large (the vexillum or standard), two lateral petals (the wings or alae) and the two anterior and innermost petals are united to form a boat-shaped structure (the keel or carina), descending imbricate or vexillary aestivation. Stamens are 10, diadelphous (stamens united by their filaments so as to form two groups). Placentation is marginal (placenta forms a rigid along ventral side and ovules are arranged in two vertical rows). So, the correct answer is 'Pisum'.