Anatomy and Systematic Position of Centaurodendron and Yunquea (Compositae)

Abstract

The genera Centattrodendron and Yunquea are remarkable in that they are both "rosette trees" which have been interpreted as belonging to the tribe Cynareae (Skottsberg 1938) and are endemic to the island Masatierra in the Juan Fernandez Islands. Centaurodendron consists of two species, C. dracaenoides Johow and C. palmiforme Skottsberg, whereas Yunquea tenzii Skottsberg is the single species of its genus. The main purpose of the present study is to show how anatomical evidence bears on the systematic relationships which have been proposed on the basis of gross morphology. Because Centaurodendron and Yunquea are the only arboreseent genera referred to Cynareae, and because they show little superficial similarity to other Cynareae in vegetative characters, a study of their anatomy is desirable in determining if this is, indeed, the correct disposition of these genera. A secondary problem is created by the genus Yutnquea, which Skottsberg (1929) erected on the basis of scanty vegetative material. Although subsequent collections have furnished no flowers of this plant, which evidently flowers with extreme infrequency, anatomical data from the vegetative portions of the plant and from recently collected mature achenes appear to be decisive in assessing Skottsberg's (1929) suggestion that it should be regarded as a genus closely related to Centaurodendron. Individuals of Yunquea are rare, and the localities in which they grow are difficult of access (Kunkel 1957; Skottsberg 1953). It iray become extinct, as has so much of the autochthonous Juan Fernandez vegetation,without having been collected in the flowering state. The recent discovery (Skottsberg 1957) of Centaurodendron paalmiforme is significant, for this species shows greater similarity to Yunquea than does C. dracaenoides. Moreover, anatomical characters can be used in contrasting the two species of Centaurodendron.