General Features

The variety of forms found among angiosperms is greater than that of any other plant group. The size range alone is quite remarkable, from the smallest individual flowering plant, probably the watermeal (Wolffia; Araceae) at less than 2 millimetres (0.08 inch), to one of the tallest angiosperms, Australia’s mountain ash tree (Eucalyptus regnans; Myrtaceae) at about 100 metres (330 feet). Between these two extremes lie angiosperms of almost every size and shape. Examples of this variability include the succulent cacti (Cactaceae), the fragile orchids (Orchidaceae), the baobabs (Adansonia species; Malvaceae), vines, rosette plants such as the dandelion (Asteraceae), and carnivorous plants such as sundews (Drosera; Droseraceae) and the Venus flytrap (Dionaea muscipula; Droseraceae). To understand this vast array of forms, it is necessary to consider the basic structural plan of the angiosperms.

The basic angiosperm form is woody or herbaceous. Woody forms (generally trees and shrubs) are rich in secondary tissues, while herbaceous forms (herbs) rarely have any. Annuals are herbs that complete their growing cycle (growth, flowering, and death) within the same season. Examples of annuals can be found among cultivated garden plants, such as beans (Phaseolus and other genera; Fabaceae), corn (maize, Zea mays; Poaceae), and squashes (Cucurbita; Cucurbitaceae), as well as among the wildflowers, such as some buttercups (Ranunculus; Ranunculaceae) and poppies (Papaver and other genera; Papaveraceae). Biennials are also herbs, but, unlike annuals, their growing cycle spans two years: the vegetative (nonreproductive) plant growth takes place from seed during the first year, and flowers and fruit develop during the second. The beet (Beta vulgaris; Amaranthaceae) and carrot (Daucus carota; Apiaceae) are well-known biennials.

A perennial grows for many years and often flowers annually. In temperate areas the aerial parts of a perennial die back to the ground at the end of each growing season and new shoots are produced the following season from such subterranean parts as bulbs, rhizomes, corms, tubers, and stolons.