Plant Culture Equipment.

A detailed description is presented in this paper of small sand and water culture equipment. A number of large out-of-doors sand cultures both for tree and annual crops have also been constructed at the U. S. Regional Salinity Laboratory, Riverside, California. In their general features these latter cultures are like those described in an earlier publication (3). The more significant modifications are discussed. The same principle of operation is used in all of the sand culture equipment. Briefly stated, each sand culture consists of a sand bed and a solution reservoir. Nutrient solution is pumped from the reservoir onto the surface of the sand at hourly or other selected intervals. The solution applied to the surface of the sand displaces to the reservoir a large part of the solution remaining in the sand from the previous flushing. Drainage to the reservoirs is provided by the use of a permeable aluminum silicate material manufactured in the form of bricks for the insulation of furnaces. These bricks (or discs) confine root growth to the sand and thus prevent the stoppage of drains. Inasmuch as the intervals of application of solution to the sand are controlled by time clocks, a minimum of manual attention is required. Small sand cultures