Observations have been made on the influence of humidity on spore germination, the rate of elongation of the germ tubes and the production of asexual and sexual fructifications of various mould fungi. The humidity range at which the different species developed is given. Some of the Mucorales and certain pathogenic moulds required high humidities (100‐93%) for their successful growth. Penicillium spp. had a wider humidity range (100‐80%). Aspergillus spp. were able to grow under conditions of even more restricted moisture supply. Spores of members of the A. glaucus group, particularly, germinated and developed at humidities as low as 70‐64%. The reasons for variations in the humidity range of the different species are discussed. The influence of the supply of nutrients on spore germination and subsequent mould growth is considered.

With Plate 6 and 6 Text-figures)The literature relating to the growth of moulds at different humidities is surveyed.Observations were made on the development of mould growh on six widely different types of feeding-stuffs for storage periods extending over some 31 years. The main factors controlling mould growth were found to be : I . Thc relative humidity rather than the moisture content of the food. 2. The length of the rtoruge peziod. Mould growth took place relatively quickly on all feedhg-stuffs stored at 100-75 % R.H. Below 75 R.H. mould growth, while not prevented, only developed after a very prolonged latent period. Mould development was observed on locust beans exposed to a humidity as low as 65 "/o after a latent period of over z years.3. The b a k e and type of nutrients provided by the various feeding-stuffs mas shown to influence the latent period as well as the extent of mould deterioration. This was confirmed by experiments on artificially dried grass fractions and by experiments on starch, protein and fibre mixtures.4. The tempnaiure of rtoruge was found to affect the rate of mould development; mould growth developed sooner on samples stored a t zz°C. than at 15.5'C.5. The type o j mould rpecier present. At high humidities all mould species grew rapidly: at low humidities, only a few types were capable of growth.

Isolations were made of mould species actively growing on a variety of feeding stuffs stored at fixed humidities between too and 65% for periods of up to 4 years. The factors influencing the species of moulds isolated were: (1) die relative humidity of the atmosphere; (2) the length of the storage period before the isolations were made; (3) the type and origin of die feeding stuffs from which the isolates were obtained.A critical humidify existed for each species below which the development of mould spores could not take place. At relative humidities (R.H.) between 100 and 90% a large variety of moulds were able to develop. Members of die Mucorales and the Fungi Imperfecti were not isolated below 90% R.H. and, although ***Pemicillium app. flourished between 100 and 85% R.H., they were not isolated below 75% R.H. ***Aspergilhes app., on the other hand, were able to develop under conditions of very restricted moisture supply. Some members of the A. ***glaucus group were able to grow at humidities as low as 65‐70%.In general, the moat commonly occurring moulds on the feeding stuffs used in these trials were small ***ascospored species of the A. ***glaucus group, particularly A. ***repens and A. ruber. It is considered that it is these species that will most frequently cause mould damage to feeding stuffs in commercial stores.

The water uptake of a wide variety of feeding-stuffs was determined over a range of fixed humidities. It was shown that the level and shape of the water uptake curves are closely related to the amounts of soluble carbohydrate and protein present. Fibre exerts a depressing effect on the water uptake, while the value is also lowered by the presence of inert fats and non-hygroscopic ash constituents. These conclusions were conhned by direct experiments on the water uptake of samples of pure starch, protein and fibre.The results of the investigations have enabled safe limits of moisture content to be laid down, for both short-and long-period storage, below which mould growth w i l l not normally take place. These limits vary for each individual feed, representative figures being included in the paper in tabular form.

1943) have shown by metabolism trials and by experiments in vitro that urea, a readily synthesized form of non-protein nitrogen, can act as a partial substitute for protein in the diet of ruminants. The latter authors have also shown that the urea is rapidly converted into ammonia in the rumen, the ammonia being subsequently transformed into protein by bacterial action. In view of the possibility of a war-time shortage of high protein feeding stuffs it was felt desirable to determine whether urea, or other comparable non-protein nitrogen compounds, could be satisfactorily incorporated into cubed cereal mixtures. Three compounds were used in the investigation: urea, which was employed in the original metabolism trials; ammonium bicarbonate, which is more readily manufactured than urea; and ammonium sulphate, which is cheap, readily manufactured, and plentiful.In addition to studying the feasibility of incorporating these compounds into cereal cubes, it was decided to carry out observations on the keeping qualities of the cubed feeds, particularly in regard to the losses of ammonia which might take place during storage. Two factors which might influence this loss are the size of cube and the type of container in which the cubes are stored. In the present experiments the cereal feeds were therefore made up in different sizes of cubes, so that different surface areas of the mixtures were exposed, and these cubes were then stored in different types of container; some in jute sacks, others in three-ply paper bags, and others in five-ply bitumen-lined paper bags.