No abstract

The stimulating effect of copper on plant growth was noted early in the use of copper salts as fungicides. A few years ago FELIX (3) obtained improvement in the growth of certain plants on several peat soils by the application of copper sulphate, both to the soil and in solution to the leaves. ALLISON, BRYAN, and HUNTER (1) Sunflowers, tomatoes, and flax were used in these investigations. Oneliter pyrex beakers with paraffine-coated, plaster of Paris covers were used as containers for the solutions in which the plants were grown. All water used in making up the nutrient solutions was redistilled from pyrex. In the first experiment with sunflowers the salts used had been repurified for an earlier study (5) on the effects of the absence of boron on plant growth. These salts had been recrystallized from water from a copper still; this still had the usual block tin condenser. In later experiments the water used for the purification of the salts was redistilled from pyrex. The methods used for the repurification of the salts2 are described in a previous paper and will not be reiterated here.

IntroductionWhile the role of the various elements in the growth of the plant has attracted the attention of a large group of workers since the beginning of modern botany, the real function of certain of these elements still remains one of the least understood phases of plant physiology.Relatively early in the history of the investigation of the growth of plants in culture solution, certain elements were found to be "essential" while others appeared to be non-essential for the normal development of the organism. Obviously, however, it is far easier to demonstrate that an element which is required in relatively large quantities is essential than to prove that elements are not necessary at all. In consequence of the difficulty of establishing the need of plants for certain elements which are required in very small quantities, the list of the " essential" elements was very short, while by implication the list of "non-essential" elements included all

A method for growing normalSiC epitaxially on the (0001) plane of 6HnormalSiC is described. The normalSiC is grown from the vapor phase by the reaction of hydrogen with silicon and carbon tetrachlorides. Cubic normalSiC grows at temperatures between 1600° and 1775°C. In order to grow hexagonal normalSiC , the substrate surface must be polished mechanically and the temperature must be greater than 1725°C.

Volume 5, No. 2, pp. 57-81, 2 figures in text uwvmsrnr of caufqrn*