312 PROCEEDINGS OP THE AMERICAN ACADEMY 



slides and arranged on zinc stands under bell-glasses. The sporidia 

 were then carefully dropped upon the leaves, which were immediately 

 covered by a bell-gluss. The leaves under each glass were sown with 

 the sporidia of but one species, and subsequently, when it was neces- 

 sary to remoisten the slides, the bell-glasses were removed for a 

 moment only, and at no time were the leaves under more than one 

 bell-glass exposed. I also used a number of small seedlings of Poma- 

 cece, each pot being covered by a glass receiver. The seedlings were 

 supposed to be in a healthy condition, but, to serve as a check, a num- 

 ber of similar seedlings were kept on which no sporidia were sown. 

 The young plants were inoculated, either by dropping the sporidia 

 upon them, or, in cases where the leaves were not in such a jiosition as 

 to retain drops well, small pieces of the gelatinous spore-masses were 

 placed on them, it first being ascertained that the spores had begun to 

 germinate. After three or four days it was necessary to remove the 

 remains of the gelatinous masses in order to prevent moulding. After 

 the lapse of a week, at which period the germinal tubes, if ever, must 

 have made their way into the leaves, I attempted in a few cases to re- 

 move the glass receivers and continue the cultures in the open air. 

 This, however, was impossible, for the plants wilted to such an extent 

 that I was obliged to keep them constantly covered. European ex- 

 perimenters usually expose their cultures to the air after a few days, 

 but it is doubtful whether this can be done in our climate except in 

 the most flivorable cases, so great and sudden are the changes of 

 moisture and temperature. 



The following statement shows the results of the cultures made in 

 May and June, 1883. I was unable to continue my cultures, unfortu- 

 nately, in the spring of 1884, as I had intended. The names of the 

 species with which experiments were made are those given in my 

 paper above mentioned, in which the synonymy is given. 



I. Gym. fuscum var. globosum. 



May 18. Sporidia sown on 



5 seedlings of apple. 



3 leaves of Crntcegus oxyacantha. 



3 leaves of apple. 



4 leaves of Amelanchier Canadensis. 



IMay 20. Spermogonia appeared on four of the apple seedlings. 

 May 28. Spermogonia appeared on the remaining apple seedling, and 



very abundantly on the three leaves of Cratccgus. 

 June 1. Spermogonia appeared on one leaf of apple. 



