Summary

Flowering plants (angiosperms) show great diversity in external form, yet they are all built on a common plan of roots, stems, leaves, flowers, fruits and seeds. The underground root system may be a tap root (as in dicots), a fibrous root (as in monocots) or adventitious (arising from parts other than the radicle), and roots may be modified for storage, support, respiration and other functions. The stem is the ascending axis bearing nodes, internodes, buds, leaves, flowers and fruits, and it too may be modified for storage, support, protection and vegetative propagation.

The leaf is a lateral, flattened organ borne at the node, with a leaf base, petiole and lamina; leaves may be simple or compound, show reticulate or parallel venation, and are arranged on the stem in alternate, opposite or whorled phyllotaxy. Leaves may be modified into tendrils, spines and other structures.

The arrangement of flowers on the floral axis is the inflorescence, which is chiefly racemose (main axis continues to grow, flowers acropetal) or cymose (main axis ends in a flower, flowers basipetal).

The flower is the reproductive unit, made of four whorls borne on the thalamus: calyx, corolla, androecium and gynoecium. Flowers vary in symmetry (actinomorphic or zygomorphic), in sexuality (bisexual or unisexual), in the fusion of parts, in aestivation, and in the position of the ovary (superior in hypogynous, half-inferior in perigynous, and inferior in epigynous flowers), as well as in placentation. …