DIDYMELLA 



209 



DIDYMELLA (Sacc.) 



Perithecia immersed, membranaceous, asci 4-8-spored, 

 paraphyses present; spores elongated, 1 -septate, hyaline. 

 Differs from Sphaerella in having paraphyses. 



Orange-tree canker (Didymella citri., Noack) forms long 

 canker-like wounds with thickened margins on the branches 

 of orange-trees in Brazil. The first symptom of disease is the 







'"''5.'- - i-SKs?* 



/ V ''' ; - 



0&h 



FiG. 59. Venturia. pirina. i, conidial 

 form of fungus on pear leaf ; 2, conidial 

 form of fungus on pear, causing scab ; 3, 

 fruit of conidial stage, highly mag. 



shrinking and depression of a patch of bark, on which longi- 

 tudinal and transverse cracks appear. When the wound 

 becomes open, black pycnidia appear, followed by the asci- 

 gerous form of fruit. 



Pyenidia very minute, o - 2-o - 4 mm. diam., conidia colour- 

 less, fusiform, 7-9X2-2 - 5 /x, on the tips of branched conidio- 

 phores. 



Perithecia depressed globose, with a long, stout beak ; 



O 



