6 - Macromorphology

Abstract

This chapter discusses how the careful examination of anatomical details, particularly the number, arrangement, and course of vascular bundles, sometimes provides insight into the possible origin, development, modification, and function of the organs of higher plants. Morphological investigation is aimed at clarifying the homologies in diverse structures among taxa. Homologous structures or organs are based upon structural or developmental similarities that result from common ancestry. Internal structure may show the nature of organs that are obscure or that cannot be determined externally. One major source of evidence to interpret the origin, development, modification, and function of structures is the number, arrangement, and course of vascular bundles supplying these structures. When a shoot ceases vegetative growth, the apical meristem undergoes changes in growth to produce the reproductive organ. These changes are reflected in the production of the floral parts instead of leaves. The pattern of the floral vascular system may mark the former boundaries, arrangements of organs, or their parts, which are lost or morphologically obscured.