Fine Structure of Tyloses

Abstract

MICROCHEMICAL methods have shown that in several species, tylosis walls consist of more than one layer¹. The outer layer is covered by an amorphous granular material while the inner surface has a crossed microfibrillar structure². In the present investigation of Eucalyptus obliqua L'Herit. and E. miniata A. Cunn. ex Schau., it was found that at least a part of the granular material is derived from the denatured contents of the vessel, and that on extraction in 2 per cent sodium hydroxide the surface could be seen to have randomly arranged micro-fibrils, as in a primary wall. Ultra-thin sections of budding tyloses showed that, even in the early stages of development, their walls consisted of two layers. There was an outer layer, which appeared amorphous in sections, and an inner multi-lamellate layer with, at least in the more mature tyloses, very regular alternation of the direction of the microfibrils in adjacent lamellæ. This was particularly obvious in the sclerosed tyloses of E. miniata where the multi-lamellate layer contributed largely to the thickened wall. The structure of the inner layer, therefore, was quite unlike that of the secondary wall of the ray cell from which it arose, and resembled more that of some green algae such as Valonia³.