Arthur 8. Hoknk and Eleanor Violet Horne 191 



metallic lustre and orange, and on potato agar plates bright shades of 

 green and blue have appeared. 



The effect produced by these various fungi in the tissues of the apple 

 can only be outlined in very general terms. In sections through a small 

 spot, where of course there may be one fungus or two or more associated 

 fungi, the mycelium is present in the air spaces: the hyphae penetrate 

 between the cells and envelop them in a web of filaments firmly adhering 

 to the cell wall. The cells lose their hyaline character through changes 

 in the protoplasm and plastids, and become brown — the tissue is darker 

 when fungi with dusky mycelium are present. In some cases mycelium 

 is present in a hyaline zone in advance of the discoloured region. 



Special Relations of the Fungi concerned in "Spotting." 



The fungi isolated from the smallest spots (yV-i m - diam.) include 

 Pleospora pomorum 1 , Leptosphaeria vagabunda, Polyopeus purpureus, 

 P. pomi, P. recurvatus, P. aureus, Fuckelia botryoidea, Coniothyrium 

 convolutum, Alternaria grossularieae, Coryneum foliicolum, Myxosporium 

 mali and certain unidentified forms. Among these fungi are to be sought 

 those responsible for the commencement of "spotting." 



In the majority of cases small spots have yielded only one fungus, 

 for example Alternaria grossularieae (Ben's Red); Polyopeus purpureus 

 (Byford Wonder, Charles Ross, Bismarck). But spots of this category 

 even when occurring on the same apple have not always yielded the 

 same fungus, for example, the brown spots on Margil yielded Polyopeus 

 aureus; the dark brown spots, Fuckelia botryoidea; again the pale brown 

 spots on Frogmore Prolific yielded Fuckelia botryoidea; other spots, 

 Leptosphaeria vagabunda. On September Beauty two spots yielded 

 Alternaria grossularieae and two Polyopeus purpureus. Alternaria and 

 Polyopeus spots occur also on Wolf River and Grenadier. 



In some cases two or more fungi may be associated in small spots; 

 for example, Alternaria grossularieae, Polyopeus purpureus and an 

 unidentified fungus, in Byford Wonder. Here we have two fungi 

 associated which in the same variety also occur singly in spots. In a 

 spot on the variety Rev. Wilks, somewhat larger than those above 

 mentioned, certain spots yield only Alternaria grossularieae, but other 

 spots on the same apple yield the same fungus in association with 

 Myxosporium mali. 



1 For the apple varieties from which Pleospora pomorum and other fungi have been 

 isolated, see Journal of Botany, I.e. and The Gardeners' Chronicle, vol. lxviti. October 30, 

 1920, p 216. 



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