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REPEATED OUTBREAKS of the leaf spot disease of olives (Olea europaea I..J.) caused by the fungus Oycloconium oleaginum Cast., have occurred in California for the past seven or eight years. This disease is well known in Mediterranean countries and has received the attention of plant pathologists there since the middle of the last century. Although known in California for over fifty years, olive leaf spot received little attention until the recent outbreaks. In 1941 I. J. Condit' and the late W. T. Horne, of the University of California Citrus Experiment Station at Riverside, began observations on the disease at Fall Brook, San Diego County, and in 1942 conducted certain spray tests. Condit and Horne's data (not published) indicate that a material reduction in infection followed applications of bordeaux sprays. In January, 1944, we began fungicidal tests and observations on disease development at Fair Oaks, Sacramento County. The trials were conducted at this location until 1946, when the work was transferred to an orchard near Orland, Glenn County. The results of the observations and tests are presented herein. THE DISEASE Common Names. The disease has been called "bird's eye spot," "leaf spot," "peacock spot," and "Oycloconium leaf spot," the last name probably appearing most frequently in the literature. Symptoms. Although symptoms most often occur on the leaf blade, they are sometimes found on leaf petiole, fruit, and fruit stem (Petri, 1913; Berries, 1923). Condit and Horne observed lesions on fruit and fruit stems in San 1

The early stages of graft union formation in Sitka spruce [Picea sitchensis (Bong.) Carr] have been examined using light microscopy in order to determine the origin of callus between the scion and rootstock. All living, undamaged cells exposed to the environment by the process of stern preparation for grafting have been found to be capable of producing callus. The first cells to respond in this way, within two days of grafting, were the epithelial cells of severed resin canals and ray parenchyma exposed where the phloem and xylem of the seion and rootstock were cut through. Fusiform cambium cells near to the graft interface dedifferentiated into callus much later (12-15 days after grafting) by becoming rounded in transverse seetion, and by dividing horizontally to produce a large number of smaller callus cells. Most callus was produced by cells external to the cambium by dedifferentiation and proliferation of ray cells, and of parenchyma associated with severed needle traces.