164 The Plant World. 



THE PREVALENCE OF CERTAIN PARASITIC AND 

 SAPROPHYTIC FUNGI IN ORCHARDS, AS DE- 

 TERMINED BY PLATE CULTURES. 



By Frederick Adolph Wolf. 



introduction. 



Chiefly because of the numerous colonies which appeared 

 in glucose agar exposures in a grove near the Agricultural Hall, 

 Lincoln, Nebraska, the suggestion was presented to try similar 

 exposures in the orchard. It was then a question as to whether 

 the same forms of fungi were present in both places. As a result 

 of this exposure, the idea was suggested that it might be of interest 

 to make a series of exposures in the orchard at definite intervals 

 during the year, beginning with September and continuing 

 throughout the following winter and spring. 



While it is known what fungi are common upon the trunk, 

 twigs, leaves and fruit of orchard trees during the summer season, 

 or growing period, yet little or nothing has been done toward 

 the determination of what is present during the winter season, 

 the dormant period of the tree's life. This is not without a rea- 

 son, however. It m.ay be due, in part, to the fact that generally 

 no new infection occurs during the winter period. It might 

 naturally be expected, too, that while the tree is dormant the 

 fungi which attack it would be dormant. This is true only in 

 part. While there is little or no vegetative growth during the 

 winter, yet some forms develop or at least mature their perfect 

 fruits at this time. 



The plant pathologist recognizes that at particular periods 

 of the year, certain parasitic fungi are abundant. He knows, 

 too, that where sugary compounds, such as fruit, bread, jelly, 

 preserves, etc., are kept, certain cosmopolitan saprophytic 

 species abound. Then, in orchards, one might expect to find 

 parasitic forms numerous only at a particular time, while 

 saprophytic species might abound at any time. 



Most of the work of determining the presence of living 

 organisms in a certain locality or in a certain substratum has 

 been bacteriological. One investigator, K. Saito,* of the Im- 

 perial University of Tokyo, determined the number of fungus 



♦Saito: Journal of Science College, Tokyo. 18:1-53. 



