IN two previous reports ** to the Textile Foundation a plan for a general experimental survey of the numbers and kinds of micro-organisms associated with textile fibres and the biochemical changes which such organisms can induce has been outlined; a comprehensive review of the literature of cotton microbiology has been presented; the development of methods for the experimental study of the micro-flora of fibrous samples has been described; and the application of the adopted method to the microbic analyses of several groups of cotton fibre samples has been recorded and discussed. The report now presented deals with two additional fundamental applications of the same methods: (1) An experimental study of the micro-flora of commercial raw cotton fibre. (2) A review of the microbiology of wool as reported in the literature, and an experimental study of the micro-flora of high grade commercial samples of back and shoulder wool. In the case of raw cotton, 14 samples of baled fibre were studied. Thirteen of them were found to have a high degree of contamination with molds and bacteria of types common to soil, air, water, and decaying vegetable material. The micro-flora of samples taken from the periphery of bales was made up largely of resistant types of organisms similar to those previously found in samples of cotton long held in storage. The micro-flora of samples from the centre of bales more nearly resembled that of fresh seed cotton. A test of the ability of the more abundant types of organisms to damage an untreated cotton yarn when grown upon it in pure culture showed that only three molds were capable of causing gross structural damage, but the majority of mold and bacterial cultures isolated were able to cause marked discoloration. The study of wool microbiology was initiated with an exhaustive review of the literature. The complete literature of wool microbiology up to 1935 is indexed and briefly reviewed in this report. Experimental methods as developed by the use of cotton were found to be suitable for the study of wool. In the analysis of the microbic population of ten samples of back and shoulder wool 550,000 to c. 400 X 16⁶ bacteria and < 300 to 4,200 molds per gram were counted. In shoulder wool, it was found that less than 10% of the total bacterial population were spore-forming. All of the molds and many of the bacteria were typical saprophytes. A large proportion of the bacteria, however, were types which have been designated "facultative parasites" and hence might be present in wool as "native" types. Generic identifications were established as follows: Molds—Stemphylium, Oöspora, Alternaria, Mucor, Penicillium. Bacteria—Rhodococcus, Micrococcus, Sarcina, Achromobacter, Serratia, Flavobacterium, Bacillus. Yeasts—several cultures not identified. A comparison of the numbers and kinds of microorganisms on back and shoulder wools showed no contrast in the flora from the two sources. Of the bacteria isolated in pure culture, only the Bacilli were active digesters of starch, gelatin, and milk proteins. These substances were vigorously digested by the majority of the molds isolated. Growth of the pure cultures on test skeins of a clean worsted yarn yielded the following results: 1. One or two non-sporulating, pigmented cultures of bacteria caused staining but no structural damage. 2. Of 35 pure cultures of Bacilli, 9 caused disintegration of the fibre but little discoloration. 3. Among the molds, Alternaria, Stemphylium, and Oöspora caused rapid discoloration and loss of strength. Other mold types were destructive but less active. A series of observations on a single lot of wool in process indicated that scouring caused important changes in the micro-flora of raw wool, in that most of the non-spore-forming bacteria and the most actively destructive molds were either removed or inactivated. A large proportion of the highly destructive Bacilli, however, remained viable in the wool after scouring.