Abstract
The present paper deals with two species of Alternaria injurious to cotton fibres in nearly ripe balls, found in last season in western Japan. One of them attacks cotton leaves, balls and cotton fibres in balls, and the other mostly cotton fibres. According to the characters of the both fungi, the former species can be referred to A. macrospora ZIMMERMAN and the latter may possibly be A. gossipii (JACZ.)
Cotton fibres in balls in various degrees of maturity, commercial cotton and absorbent cotton were inoculated with the pure cultures of the Alternaria under consideration. With the exception of the absorbent cotton, discoloration or blackening of the cotton fibres inoculated was observed.
The relation of temperature and hydrogen ion concentration to the growth of the both species was studied. It was found that the minimum; optimum and maximum temperatures for the mycelial growth of the both fungi were same and about 5°, 27-30° and 36°C., respectively. The acid limit for the mycelial growth of the both fungi was about pH 2, the alkaline limit seemed to be slightly above pH 10. The optimum hydrogen ion concentration for the growth was about pH 5.
