THE FUNGI WHICH CAUSE PLANT DISEASE 



265 



asci subclavate, fugaceous, 55-70 fi; ascospores allantoic!, 12- 

 22 X 3-5 yn; conidial stage ( = Gloeosporium rufomaculans) with 

 small sori, developing in more or less concentric circles, usually 

 soon rupturing and pushing out spores in small pinkish masses; 

 spores hyaline to greenish, 

 chiefly oblong, unicellular 10- 

 28 X 3.5-7 M- 



The conidial stage of this 

 fungus was first described by 

 Rev. M. J. Berkeley in 1854 

 as a Septoria. It was later 

 transferred to the form genus 

 Gloeosporium under which 

 name the literature pertaining F'g. 193.—?. perithecium of G. rufomacu- 



... . 1 c l^ns showing asci in aitu; 6, asci show- 



to it IS largely to be found. ing detail. After Spaulding and von 



See Southworth.250 The as- ^'^^'^''^■ 



cigerous stage was found by Clinton "''^ in 1902 and the fungus 

 described as a Gnomoniopsis. In 1903, it was given the present 

 name. A bibliography of some one hundred eighty titles is 

 given by Spaulding and von Schrenk.-'*' 



The conidia germinating on apples send germ tubes through 

 the skin, usually through wounds, occasionally through a sound 

 surface.-^' The mycelium grows subepidermally, branching 

 rapidly, intercellularly and intracellularly, 

 absorbing the sugar and other nutrients 

 present, and resulting in brown discolora- 

 tion of cells and dissolution of their connec- 

 tion with neighboring cells. The mycehum 

 is first hyaline but later, especially in the 

 stromata, it may be quite dark. Acervuli 



Appressoria produced appear, often in concentric rings, lift- 



by germinating spores. ^'f i o > 



Aiter Spaulding and ing the epidermis with their palisades of 

 conidiophores. The latter, at first hyaline, 

 later olivaceous, bear the numerous conidia, which are pinkish, 

 rarely cream-colored, in mass. In germination the conidia be- 

 come uniseptate and often on the tips of the young mycelium 

 develop the dark thick-walled irregularly shaped spore-like struc- 

 tures, so common on the sporelings of the Melanconiales. These 



Fig. 194.— G. 



