ANTHRACNOSE OF CUCURBITS. 



25 



As a result of the examination of a considerable number of these 

 preparations, it was found that within 24 hours after inoculation 

 appressoria had been formed in abundance, usually one to each spore 

 sessile, or on short germ tubes. These were particularly numerous 



Fig. 1. — Surface view of a portion of a cucumber-leaf epidermal cell, showing appressoria and penetration 

 tubes, six days after inoculation. In five instances the empty spore case is shown lying near the 

 appressorium. The circular germ pores can be seen in the appressoria. Two appressoria (upper right) 

 have formed short penetration tubes. Another has produced considerable mycelial growth within the 

 host cell. (Camera-lucida drawing; magnified about 395 times.) 



in the vein depressions and in the depressions bounding the epidermal 



cells. No signs of host penetration were found in this material or in 



material fixed 44 hours after inoculation. 



In leaf areas fixed 65 hours after inoculation, penetration tubes 



were commonly visible within the epidermal cells underneath the 



appressoria and a 

 small round pore 

 was visible in the 

 wall of the appres- 

 sorium next to the 

 host cuticle (fig. 1). 

 Hasselbring noted 

 similar pores in the 

 appressoria of the 

 apple bitter-rot 

 fungus. In mate- 

 rial fixed 121 hours 



Fig. 2. — Surface view of epidermal cells of a cucumber leaf , showing intra- 

 cellular mycelium from three appressoria, six days after inoculation. 

 (Camera-lucida drawing.) 



after inoculation, 



when macroscopic 



symptoms were 



already apparent, the penetration tubes were found under a large 



percentage of the appressoria, and in many cases considerable 



mycelium was found in the epidermal cells underneath (fig. 2). 



69806°— 18— Bull. 727 4 



