As indicated by both size and longevity of some vascular plants, the apical meristem is indeterminate . Its activity of producing cells, or laying the bricks of the plant body, can continue indefinitely. The apical shoot meristem also has the capability to produce secondary centers of meristematic activity, lateral meristems . The lateral meristems provide a structural groundplan for mapping the angiosperm shoot. Shoot tissue that extends between these points is knowned as the internode .
Most angiosperms lack a vascular cambium, i.e., they are non-woody herbs or herbaceous .
Both woody and herbaceous angiosperms can show indeterminate apical meristem activity and a perennial life style. Herbaceous perennials living in temperate or seasonable parts of the world sacrifice 'above ground' tissue during the difficult season but often retain dormant meristems and photosynthate in a tough, underground structure known as a caudex . Summer annuals germinate in the Spring and pass the Winter as seed whereas Winter annuals germinate in the Fall, flower in the Spring, and pass the dry Summer season as either seed or fruit. Many key players in the remarkable Texas Spring flora are Winter annuals that are in full vegetative growth during December and January. Thus, it is important to insure that the sample collected includes a 'below ground' component.