Measurements of the rate of growth of Sporotrichum carnis on Czapek's agar indicate that:
1. The optimum temperature for growth is at 25° C.
2. Growth can take place at 30° C., but is restricted and unusual shapes are produced by the thickening of the germ tubes.
3. Fairly good, though slow, growth was obtained at - 5° C. on supercooled agar, and growth also took place at - 7° C. on supercooled agar. There are indications, however, that growth is somewhat restrained at - 5° C.; the germ-tubes become thicker and curl more readily than at higher temperatures.
4. In no case was growth observed on frozen agar during the periods of incubation of the slides--up to two months.
5. A curve is given showing the relation between temperature and rate of growth during the logarithmic phase. The form of the curve suggests that growth on supercooled agar becomes infinitely slow at - 10° C.
6. Application of the Arrhenius-van't Hoff equation to the results obtained is considered.
The author wishes to express his thanks to Dr G. S. Graham-Smith, F.R.S., for his interest in this work.