34 CEANBEERY DISEASES, 



this genus is very peri^lexing. The differences in the morphological 

 characters of the ascogenous fructifications are quite as slight and 

 unsatisfactory for separating species as the differences which occur 

 in the conidial forms. This has been clearly shoAvn by the studies of 

 Shear and Woods."^ Various inoculation experiments made with the 

 conidial forms occurring on different hosts have seemed to indicate 

 that they will pass readily from one host to another. Most such 

 inoculation experiments appear to us inconclusive, particularly in 

 such cases as those given by Halsted ^* and others, in which transfers 

 of conidia were made from one mature fruit to another by inserting 

 the conidia in the fruit. These experiments may perhaps be more 

 correctly interpreted as indicating that the fruit upon which the 

 fungus grows successfully in such an inoculation experiment is 

 simply a satisfactory nutrient medium for the fungus. In order to 

 demonstrate the possibility of the various forms being passed from 

 one host to another as actual parasites, it would be necessary to make 

 the inoculations on the living and actively growing parts of the 

 plants. This has been done in one case, at least, by Sheldon,*^ in 

 which he successfully inoculated stems and leaves of growing sweet 

 peas by applying conidia from the bitter-rot {Glomerella rufomacu- 

 lans (Berk.) Spauld. & von Schrenk) of the apple. Whether other 

 forms will show equal ability to pass from one host to another as 

 active parasites remains to be determined. 



Dormant condition of the fungus. — AVe have found by experiments 

 similar to those described in connection with the accomit of the 

 scald fungus, Guignardia vaccinii (p. 21). that the mycelium of the 

 cranberry Glomerella may remain in an inactive or dormant condition 

 in the tissues of the living fruit of the cranberry for a considerable 

 time. '\^liether the fungus is really inactive or not it is difficult to 

 sa}'. It at least does not give the slightest local external evidence of 

 its presence. Berries which were, so far as could be determined by 

 external examination, perfectly sound and free from fungi, were very 

 thorouofhlv soaked and washed in a 1-500 solution of corrosive sub- 

 limate. Such leaves and berries when placed in warm, sterile, moist 

 chambers developed typical cases of anthracnose. On the leaves 

 treated in the same manner numerous acervuli have appeared, 

 and cultures made from the mycelium found in the decayed fruits 

 mentioned above have produced the conidia in pure cultures. Inoc- 

 ulation experiments, made by applying fresh conidia to the surface 

 of cranberries and aj)ples placed in warm moist chambers, have been 

 without definite results. It seems that in the case of this fungus, as 

 well as Acanthorhj-nchus and Guignardia, the spores do not pos- 

 sess the power of penetrating the epidermis of the fruit after it has 

 reached maturity. Infection apparently occurs earlier in the season, 



110 



