THE MONTHLY BULLETIN. 



531 



until a chain of four conidia, with a short pedicel at the base of each, 

 has been formed. This characteristic distinguishes this fungus from the 

 Macrosporium and places it in the genus Alternaria. 



Under favorable conditions conidia may be produced in forty-eight 

 hours after transfer of a portion of mycelium from a pure culture to a 

 plate or tube of sterile nutrient agar. Each cell of the conidia is capable 

 of giving rise to a hypha. 



Fig. 326. — Conidia and mycelium of Alternaria citri. (Original.) 



Inoculations of Oranges From Pure Cultures of Alternaria citri. 



A large number of sound oranges were inoculated with spores or 

 mycelium taken from either pure cultures made from affected oranges 

 or directly from such oranges. Oranges from. Fairoaks, Oroville, 

 "Whittier, Covina and Ensenada, Mexico, were used in the work. 



Oranges were prepared for inoculation by being washed in 40 per 

 cent formalin and, if cut, a sterile knife was used for that purpose. 

 All moist chambers used were first washed with hot water and soap,, 

 and then rinsed out with 40 per cent formalin. 



Spores were placed well into the navel in one series of experiments. 

 No wounds were made in the tissues and no moisture was added. The 

 purpose of this experiment was to ascertain if infection would take 

 place simply through the lodgment of spores in the navel end. The 

 structure and condition of the tissues of the navels were not known 

 until after the oranges were cut open, which was about three weeks 

 later. Green and mature oranges were used. When cut open, as stated, 

 it was found that infection had not taken place in any case. No open- 

 ings or imperfections of the navel tissues were found in these oranges. 



In another series of experiments inoculations were made in the 



3— HO 



