This work describes the general, macroscopic and microscopic characteristics of the wood of Acanthosyris spinescens (Mart. Et Eichl.) Gris., A species known in Rio Grande do Sul as a bull shade. Quantitative data are provided on the cellular constituents of the wood and photomicrographs of the wood. The anatomical structure is compared with literature information for the genus Acanthosyris and family Santalaceae. The curious radial structure, composed mostly of multi-series rays that separate in smaller units, with aggregates of rays and surrounding cells, is analyzed for its ontogeny.
