OF ARTS AND SCIENCES. 315 



VIII. Gym. clavipes. 



May 25. Sporidia sowu on 



1 seedling of Cratcegus Douglasii. 



1 seedling of Pi/rus cult. 

 May 31. Sperraogouia appeared ou seedling oi Pyrus. 



A third set of experiments consisted in placing fresh shoots of Ame- 

 lanchier Canadensis and Fyrus arhutifolia in jars of water, covering 

 them with receivers, and sowing on the leaves the sporidia of G. ma- 

 cropus, G. clavipes^ G. biseptatum, and G. Ellisii. The cultures were 

 started on May 30th, with the following result. On June 4th, spermo- 

 gonia appeared on both Amelanchier and Pyrus arhutifolia sown with 

 the sporidia of G. macropus and G. clavipes, and on Amelanchier sown 

 with G. biseptatum. 



As the sporidia of G. biseptatum and G. Ellisii proved more refrac- 

 tory than those of other species, two supplementary cultures were 

 made, as follows : — 



Gym. biseptatum. 

 May 29. Sporidia sown on 



5 leaves of Pyrus arbutifolia. 

 3 leaves of Nescea verticillata. 



Young shoots of Nes(Ea, Amelanchier, and Pyrus arhuti- 

 folia. 

 May 31. Spermogonia appeared on leaves of Amelanchier shoot. 



Gym. Ellisii. 



May 29. Sporidia sown on 



5 leaves of Pyrus arbutifolia. 

 3 leaves of Nescea verticillata. 

 Young shoots of Pyrus arbutifolia and Nescea. 

 No spermogonia. 



In these last two cultures I was led to try the leaves of Pyrus arbu- 

 tifolia because the form known as Rcestelia transformans had been 

 usually found by me in districts near Cupressus thyoides, on which G. 

 biseptatum and G. Ellisii are parasitic. As I had never succeeded in 

 getting spermogonia from sowings of G. Ellisii on Pomacece, it occurred 

 to me that possibly the a3cidial form of that species might be found on 

 a host of some other order, and, in the cedar swamps where G. Ellisii 

 is found, Nescea abounds and is not infrequently infested with the 



