OF ARTS AND SCIENCES. 263 



May 18. Spermogonia appeared on each Crataegus. 



May 30. Signs of aacidia on all the leaves affected, localized on the 

 midribs and veins. 



June 2. Peridia began to show, which in about a week developed a 

 Rcestelia, having the microscopic characters of lacerata (the form 

 subsequently spoken of as lacerata, x), while the peridia were but 

 slightly lacerate and resembled those obtained from the macropus 

 culture before exposure to the weather. With the remaining 

 plants no result was obtained. 



G. GLOBOSUM. 



April 30. Sporidia sown on 



3 Cratcegus coccinea. 

 3 Pyrus Americana. 

 3 Pyrus mains. 

 May 9, Spermogonia appeared abundantly on all the Cratcegus 



plants, on a single leaf of Pyrus Americana, and on one apple. 

 May 1 6. All plants that had not produced spermogonia were rein- 

 fected without result. 

 June 2. Sporidia sown on 



1 Amelanchier Canadensis. 



June 12. Spermogonia on Amelanchier, not in great abundance. 

 This plant was accidentally destroyed late in June, at which time it 

 showed no signs of Eecidia, while the remaining plants affected con- 

 tinued to produce spermogonia until late in July, when the leaves 

 withered and fell off. 



G. BISEPTATUM. 



May 30. Sporidia sown on 



2 Amelanchier Canadensis. 

 1 Pyrus arhutifolia. 



June 12. Spermogonia on both Amelanchiers, the Pyrus not affected. 

 Towards the end of June there were slight indications of pecidia in 

 most of the affected leaves. The development of the Rcestelia was 

 very slow ; and though the bulbous base of R. hotryapites was re- 

 cognizable in August, it was not until early in October that peridia 

 were developed having the appearance and microscopic characters 

 of hotryapites. 



