The Wood Anatomy of Schouwia purpurea subsp. arabica and Fabrisinapis fruticosus (Cruciferae)

Abstract

Schouwia is a desert plant which is reported to be annual but it may perennate if subjected to grazing pressures. It grows in large stands, and is of economic importance, providing food and shelter for the desert locust Schistocera gregaria Forssk. Its habitat is one which is only periodically supplied with rain water, and the plants grow very slowly. Locusts usually visit the plants when they have developed new leaves about a month after rain. Schouwia schimperi Jaub. & Spach (S. purpurea subsp. schimperi (Jaub. & Spach) Muschler), grows in Egypt, Nubia, the southern Sahara, Mauritania, and Arabia Petraea. Its wood has previously been described (Messeri, 1938), but that of S. purpurea subsp. arabica (Vahl) Maire which occurs in the central Sahara and south Arabia has not. Fabrisinapis fruticosus C. C. Townsend was recently discovered by J. J. Lavranos & A. Radcliffe-Smith on Socotra. The plants are shrubby perennials. The wood anatomy of this species is described here for the first time. The family Capparaceae, regarded by Hutchinson (1959) to show parallel evolution with Cruciferae, has many woody members. The wood of some of these species which grow in similar conditions to Schouwia is compared with the cruciferous wood.