WOUND-TUMOR is a plant disease caused by a virus, Aureogenus magnivena Black, known to be transmitted by the insects Agallia constricta Van Duzee, Agalliopsis novella (Say) and Agallia quadripunctata (Provancher) (Black, 1944). There are at least 43 species of higher plants belonging to 20 families which are known to be susceptible to the disease (Black, 1945). The most common symptoms of wound-tumor are enlargement of the leaf veins and the production of tumors on the roots. Kelly and Black (1949), in studying the origin and development of root tumors in sweet clover, Melilotus alba Desr., found that the tumors develop by abnormal cell multiplication and originate principally in the pericycle. The purpose of the present investigation was to determine the staining properties and chemical nature of certain inclusion bodies found in the cytoplasm of root tumor cells of sorrel (Rumexn acetosa L.). The term spherule is proposed as a name for these bodies. The spherules were briefly mentioned in earlier papers (Black, 1946, 1947; Littau and Black, 1949) as inclusion bodies. MATERIALS AND METHODS.-Tumors produced on the roots of infected sorrel plants were used for this study because the spherules were first noticed in this species, and because earlier observations showed that spherules were numerous in sorrel root tumors. Young seedlings were inoculated with the virus by allowing a colony of 5 viruliferous insects (A. constricta) to feed on each plant for 7 days. After symptoms developed, small sections of root, each bearing a tumor about 3 mm. in diameter, were removed, placed in fixing fluid, dehydrated and infiltrated by the tertiary butyl alcohol method (Johansen, 1940), and embedded in Turtox paraffin or Tissumat. A variety of fixing fluids were used, namely: Fleming's strong chrom-osmo-acetic (referred to hereafter as Flemming's fluid), formalinaceto-alcohol (FAA), Navashin's, Carnoy's alcoholacetic, Carnoy's alcohol-acetic-chloroform, 10 per cent formalin, alcohol-acetic acid-cerium nitrate (Bald, 1949a,b), and Allen and Wilson's modification2 of Bouin's fluid.