532 



THE MONTHLY BULLETIN. 



navels of ten oranges after making stabs into the navel tissue with a 

 sterile knife. Upon examination, three weeks later, the fungus was found 

 to have developed in five oranges out of the ten, producing the typical 

 black rot with the characteristic spores and mycelium of Alternaria 

 citri, while in the other five oranges the fungus failed to develop. It is 

 possible that in the latter the spores were not lodged in the wounds and 

 failed to germinate on account of lack of moisture. 



In a series of experiments, extending over a period of about one year, 

 twenty-two oranges were cut in half and each half inoculated with 

 spores or mycelium from pure cultures made from affected oranges. In 

 all cases the oranges were first washed with formalin and placed in 



Fig. 327. — Germinating conidia showing the tubercles on the surface. Also showing 

 character of mycelium. Magnified 1,000 times. (Original.) 



sterile moist chambers. But two cases out of the forty-four inoculated, 

 failed to develop the characteristic black rot of Alternaria citri. All 

 cultures, (half oranges) which did not become contaminated with Pen- 

 cillium species or Mucor mucedo, finally became black over the entire 

 surface, including the peel. (Fig. 328.) 



Cultures were made from these artificially inoculated oranges and 

 produced the characteristic spores and mycelium of Alternaria citri. A 

 large number of sound half oranges were, prepared as in the previous 

 experiment, and inoculated with spores of mycelium from these cul- 

 tures. All these inoculations were successful in producing the char- 

 acteristic black rot of Alternaria citri and the typical spores and myce- 

 lium of the same. 



