Abstract
According to the publication by the Committee on Nomenclature, I. A. W. A. (Glossary cf terms used in describing wood, 1933), three types of wood rays are recognized. In this they described a homogeneous ray as “a xylem ray composed of radially elongated cells” and a heterogeneous ray as “a xylem ray composed of cells of different morphol gical types, typically with the cells of the multiseriate part radially elongated and those of the uniseriate parts vertically elongated or square”.
It wouid now appear that, after seventeen years, it is time that these definitims should be amended, for in the intervening years much intensive anatomical work has been accomplished, and workers in many parts of the world are finding it increasingly difficult to accept these definitions. Objections to them have been pointed out from time to time.
It is clear from the examples given by Dr. M. M. CHATTAWAY how very inexact the present terms are, and how difficult to apply, even for descriptive purposes.
A suggested altaration of CHATTAWAY is:-
Homogeneous ray “a xylem ray in which all the cells which are contiguous to the same elements are morphologically or functionally similar”.
Heterogeneous ray “a xylem ray composed of cells which, when contiguous to the same elements are composed of cells of different functional or morphological types”.
