1. Six types of surface discolorations are described and a list is given of the fungi causing these discolorations. The fungi listed are shown to be capable of reproducing the discolorations under experimental conditions.

2. The surface moulding of butter is shown to depend largely on the weather conditions at the time of removal from cold store (temperature and humidity), and the foodstuffs available from the wrapping materials.

3. The butter, boxwood and parchment are capable, in the presence of free water, of supplying substances which stimulate the germination of fungal spores.

4. The water-soluble extract of parchment stimulates fungal germination and growth. Its value as a nutrient is masked when parchment is in contact with butter. Even a well-washed parchment is capable of supporting fungal growth.

5. The butter and the boxwood are even more important as sources of soluble food material than parchment of high “water-soluble” content.

6. Glycerine is a source of food for fungi and a glycerine-softened parchment is more liable to mould attack than a glycerine-free paper.

7. It has been shown that the softening of parchment with salt does not prevent mould attack. Two strains of Cladosporium herbarum and Penicillium sp. attacked salt-softened parchment more easily than untreated parchments.