The composition of a medium is described that proved useful to culture callus of a variety of monocotyledonous and dicotyledonous plants. Growth on the medium was often better than on some other excellent media. In addition to supporting rapid cell growth, a soft, friable type of colony growth was often obtained. This type of loose, friable cell growth facilitated work with single cells and the enzymatic removal of cell walls in related studies. A high level of auxin-type growth-regulating substances (AGRS) generally favored cell cultures of monocotyledonous plants, while low levels of cytokinin were essential for most dicotyledonous cell cultures. Some cultures of dicotyledonous plant cells adapted to a cytokinin-free medium containing a high level of 2,4-dichlorophenoxyacetic acid (2,4-D) or p-chlorophenoxyacetic acid (pCPA). The preferred AGRS were 2,4-D and pCPA. Citrate, succinate, and 2(N-morpholino) ethane sulfonic acid (MES) were effective medium buffers, but phosphate alone seemed adequate to buffer the medium at pH 5.8–5.9.

er drops were allowed to fall vertically. The collisions took place in an electric field of 600 volt/cm. By moving the position of the hole in the bottom plate with respect to the point of collision, it was possible to capture independently, in the Faraday cage below, the large majority of either the larger or the smaller secondary drops.We discovered that both of these fractions were highly and equally electrified but that the charges were of opposite sign. Specifically, the larger secondary drops acquired a charge of the same sign as that on the top plate, while the smaller drops had the same charge sign as the bottom plate. The larger drops always fall faster in the free atmosphere, so that once the direction of the inducing electric field E is specified, the arrangement of positive and negative charges is determined. Our measurements show that the induced free charges, Q, in electrostatic units on the oppositely charged fractions are

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Growth, nutrition and chlorophyll development were studied in chlorophyllous callus tissues isolated from the following edible angiospermous plants: carrot root, crown gall of tomato, endive embryo, leaf petiole and stem of lettuce, leaf petiole of parsley, pea stem and rose stem. Growth patterns of these tissues in vitro were sigmoid. Synthetic media produced less growth, in terms of fresh weight increase, than media containing coconut milk, a highly complex and little understood natural substance. MURASHIGE and SKOOG'S synthetic medium proved useful for satisfactory growth and chlorophyll production in a number of tissues. Its usefulness was further increased by additional amounts of copper sulphate, potassium nitrate and monobasic ammonium phosphate. Increased levels of iron and magnesium inhibited growth. Incorporation of yeast extract in the tobacco-high-salts-medium produced the highest amount of growth and chlorophyll formation in endive tissue. Presence of exogenous sucrose was essential for the continued good growth of the above callus tissues in vitro. Highest amount of growth took place either in white light or in the dark. Different tissues had different responses to high or low intensities of light. Endive and carrot tissues produced in vitro were palatable to human taste. Endive tissue was particularly good as it also differentiated many small rosettes of leaves, shoots and had a mild aromatic flavor typical of the endive plants grown in nature.