192 The Plant World. 



In an exposure made October 30th, during a drizzling rain, 

 no Phyllosticta appeared. The only period of any length 

 when it was not secured was during February. On February 

 2nd, two days following a heavy fall of snow, when the trees were 

 still laden with snow, no Phyllosticta was found. Only a few 

 colonies of Cladosporium and Alternaria appeared. Before the 

 next exposure, February 8th, there had been another snow and 

 the ground and trees were again covered. This time only a few 

 colonies of Cladosporium and Penicillium appeared. Because 

 of inclement weather no exposures were made until February 

 27th. At this time the plates again contained a good seeding 

 of Phyllosticta. Since then it has appeared, without fail, in 

 every set of exposures. 



There are those who hold that the Fungi Imperfecti, to 

 which Phyllosticta belongs is an artificial group, which will be 

 merged into the natural groups as the complete life histories are 

 determined. A form with such extremely resistant spores would 

 seem to require no perfe^i stage. The chances are that it has 

 no other stage than the pycnidial and so can never be merged 

 with those forms which produce perfect fruits. The pycnidial 

 form is so well adapted that no other is necessary to insure the 

 maintainence of the species under adverse circumstances. If 

 it ever had a perfect stage it has probably ceased to function. 



(c) Cultural Characters. — In cultures on glucose agar, Phyl- 

 losticta limitata has a very characteristic appearance, forming a 

 deep red pigment, at first faintly pink, but deepening as the 

 colony matures. In slant tubes on this medium pycnidia were 

 formed last October and November. They were produced 

 evenly over the surface and slightly immersed. When the pycni- 

 dia were placed on a slide with a cover-glass over them, the 

 hyaline spores formed coiled strands extending the entire length 

 of the microscopic field, indicative of the copious spore pro- 

 duction. 



{d) Inoculations. — Since there has been some doubt as 

 to the parasitism of Phyllosticta limitata, the fungus was used 

 for inoculation experiments. The hyphae were used for inocu- 

 lation on apples that had been carefully sterilized with mercuric 

 chloride solution. In the course of eight days they produced 

 spots of rotted tissue one-half inch in diameter. 



