1. Substantial control of covered smut of wheat, Tilletia caries, was obtained when seed was treated with an approved organo-mercury seed disinfectant using both rotational and gravitational machines for mixing.

2. Good control of leaf spot of oats, Helminthosporium Avenae, was also obtained, using an approved organo-mercury seed disinfectant and mixing grain and powder together in a model rotational-type machine.

3. The model rotational machine gave an even mixing of grain and seed disinfectant with as few as forty-eight turns. Twenty-four turns was almost as effective but the mixing was much less even.

4. The gravitational machine was not so efficient in producing an even mixing as the rotational machine as assessed by the control of covered smut of wheat.

5. There was an indication that the rotational machine gave a better disease control.

6. Improvement was effected in the efficiency of mixing with the gravitational machine by the addition of a felt lining to the feed hopper.