Steinhart, C. E., L. C. Standifer, Jr., and F. Skoog. (U. Wisconsin, Madison.)Nutrient requirements for in‐vitro growth of spruce tissue.Amer. Jour. Bot. 48(6): 465–472. Illus. 1961.—Callus derived from seedlings of Norway spruce has been cultured for 3½ yr on a medium supplemented with malt extract. The responses of the callus to auxin, kinetin, light intensity, and pH were determined. The malt extract employed was fractionated by various methods, and it was shown that the active fractions were generally ninhydrin positive. The free amino acid composition of the extract was determined. Malt extract could be replaced completely by casein hydrolysate. Arginine, glutamine, or urea, although less effective, also supported continuous growth of the callus. In contrast, NH4NO3as a sole source of nitrogen failed to support growth. The same compounds that supported growth of the established strain of callus also stimulated initial formation of callus from seedlings. Inositol was the only vitamin that could be shown to stimulate callus growth. A synthetic medium has been developed for the cultures; it includes inorganic nutrients, naphthaleneacetic acid, kinetin, myo‐inositol, and either arginine or urea. Thiamin, choline chloride, and cystein are also added to the medium, although a requirement for the latter 2 of these 3 compounds has not been demonstrated.