DORMANT CONDITION OF THE FUNGUS. 21 



races, or generations which causes it to produce the ascogenous stage 

 whenever conditions for its growth are favorable, i. e., on favorable 

 culture media without special reference to their exact composition 

 or environment or on the leaves of its natural host. Whether this 

 potentiality depends on some preceding union of nuclei from dif- 

 ferent or the same individuals, or some equivalent stimulus, we are, 

 of course, unable to say. It appears possible, however, that there 

 may be such a factor concerned. 



DORMANT CONDITION OF THE FUNGUS. 



Leaves and berries which, so far as can be discovered by external 

 examination, are perfectly sound are very frequently found to con- 

 tain the fungus. Leaves perfectly normal in appearance, taken from 

 vines growing in diseased areas, have been thoroughly washed and 

 soaked from fifteen minutes to two hours in a solution of corrosive 

 sublimate, 1 part to 500 parts of water, in order to destroy any 

 fungous spores which might possibly be present upon their surfaces. 

 These leaves were then placed in sterile, moist chambers. After a 

 period of eight to twelve days an abundance of the pycnidia of 

 Guignardia raccinii was found to have developed upon the leaves, and 

 in some instances these were followed by the ascogenous form of the 

 fungus. Berries apparently perfectly sound and healthy have also 

 been treated in the same manner, and in many cases the characteristic 

 decay of the fruit has followed. Cultures made from the pulp of 

 these berries have produced the fruiting forms of the Guignardia. 



So many experiments of this kind have been tried that we feel 

 convinced that the fungus must be present within the tissues of the 

 leaves and berries referred to in a dormant or more or less inactive 

 condition. It does not seem possible that any spores could resist the 

 action of the corrosive sublimate solution used. Tests which have 

 been made show that the spores of Guignardia vaccinii are killed 

 by being immersed in a 1 to 1,000 solution of corrosive sublimate for 

 five minutes. A great number of microtome sections of leaves and 

 fruit supposed to contain the dormant form of the fungus have been 

 studied. It has been found very difficult to demonstrate the presence 

 of the fungus and to determine its form, chiefly, perhaps, on account 

 of unsatisfactory results in differential staining. 



In case of the berries, carefully stained sections have shown what 

 appear to be cells of fungous hypha? just beneath the epidermis. In 

 both leaves and fruit the fungus seems to be able to exist in the 

 tissues in a more or less inactive or dormant condition while await- 

 ing an opportunity for further development; such opportunity is 

 apparently afforded by any conditions which weaken the cranberry 

 plant and also by those which are favorable to the growth of the 

 no 



