The course of resin canals in the shoots of conifers

Abstract

In this paper, the Araucaria type and Cunninghamia type are defined. Adult plants ofAraucaria cunninghamii andA. heterophylla show the Araucaria type, though seedlings of the latter species show the Podocarpus type. The Araucaria type is considered to have been derived from the Podocarpus type by the development of the resin canals at the adaxial corners of leaves. The pattern ofA. columnaris is a little more complicated than the Podocarpus type.A. bidwillii, A. angustifolia and three species ofAgathis have very complicated patterns.

In the Cupressaceae, shoots with needle leaves show the Torreya type. But in shoots with scale leaves, resin canals are shorter and wider. These resin canals are the so-called glands, which are apparently derived from the resin canals of the Torreya type.

Most members of the Taxodiaceae show the Torreya type. Although seedlings ofCunninghamia lanceolata show the Dacrydium type, older plants show the Cunninghamia type. The latter type can be considered to have been derived from the former by the formation of bridges of resin canals. Long shoots ofSciadopitys verticillata have the systems of central canals as well as of peripheral canals. The former system is of the Dacrydium type.