166 The Plant World. 



It is needless to say that a valuable classification of such 

 molds as Aspergillus and Penicillium must be based upon ascus 

 formation. Dr. Fr. Dierck* has said "Moulds vary immensely 

 according to the circumstances under which they are observed. 

 In Penicillium, for instance, the only hope of stable identifica- 

 tion is in cultures for several generations under rigorously uni- 

 form conditions." Since it is well known that many forms do 

 not produce their perfect fruits on glucose agar, and as it is not 

 within the scope of this article to develop methods of discover- 

 ing fruit formation, interesting as it may be, where the species 

 can not be readily determined, no species name will be given. 



Almost any fungus is liable to appear where one is making 

 trap exposures. This makes identification by hosts an impossi- 

 bility. One can only surmise that the fungi so obtained came 

 from the plants surrounding the place in which the exposures 

 were m.ade. Such identification, too, has led to almost endless 

 confusion, because of the tendency to make just as many species 

 as there are host plants. We have come to recognize that a 

 fungus can not be determined alone by the host on which it 

 occurs, since many species are cosmopolitan and omniverous in 

 their conidial or hyphomycete form. The complete round of 

 life, host, cultural characters and spore measurements all aid 

 in determining the species with which we are dealing. 



As the work progressed the constant presence of some forms 

 in the exposures and the absence of others which were known to 

 be present in the orchards, led to making exposures in other 

 orchards. From them, suggestions were obtained, valuable 

 both in themselves and in the fact that they were explanatory 

 of results obtained in other places, though no attempt was made 

 in any of these to make a regular serial set of exposures. 



DISEASES OF APPLES. 



Quite a number of diseases of apples occur in the state, and 

 many of the causal organisms are known as regards cultural 

 characters. The spores of many are known to grow upon 

 glucose agar and so might be expected to appear in the trap 

 cultures, provided viable spores were prevalent. The following 

 tabulation will place these facts before us: 



♦Thorn: Journal of Mycology. 9:117-124. 190S. 



