168 



The Plant World. 



Besides these several forms appeared in the cultures which 

 were never made to produce conidia or perfect fruits and no 

 idea as to their identity was secured. 



The "green m.old," Penicillium expansum, the "leaf-spot 

 fungus," Phyllos'Ac'a limi'atx, and ihz "Illinois apple-tree 





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xyj ,> 







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4!" 



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Fig. 1. Section of phyllosiicta limitata pyonidium, grown on glucose agar. 



canker," Ntivimularia discreta, were the only forms which were 

 found, that are ordinarily troublesome in apple orchards. 



RELATIVE ABUNDANCE. 



Perhaps no better method could be employed in giving some 

 facts concerning the relative abundance of living organisms than 

 to arrange in tabular form some of the counts of the colonies as 

 they appeared in the exposures. This fact can be as well represent- 

 edby taking into account a part of the actual counts, as if the 

 whole period during which the exposures were made was included. 

 The table covers the results of eight consecutive exposures. 



I 



