396 THE RUSTS OF NOVA SCOTIA. FRASER. 



On Cirsium arvense (L.) Scop., Pictou, Truro. 



The rust on the Canada thistle is common and widely dis- 

 tributed. The life history of the fungus has been worked out 

 by Eostrup. The mycelium hibernates in the upper part of 

 the rootstock and thus the spring shoots are infected, the 

 mycelium invading the plant. The first generation consists 

 mostly of pycnia and uredinia, the second comes from uredinio- 

 spore infection and the mycelium is localized. Ilrediniospores 

 are freely produced but no pycnia. 



The germ pore of the upper cell is placed at the apex ; that 

 of the lower cell is often some distance below the septum. 



Puccinia variabilis Grev. 



0. Pycnia not observed. 



1. Aecia amphigenous, mostly hypophyllous, usually on 

 sin all yellow or purple spots, solitary or in scattered small 

 groups ; peridium low, margin lacerate. Aeciospores sub- 

 globose or ovate, 18-22 by 22-27/*; contents orange, fading to 

 colourless, verrucose. 



IT. Uredinia amphigenous, on small yellow or purple 

 spots, scattered, small, soon naked, brown. IJredimospores 

 globose, subglobose or ovoid, 18-20 by 20-27/x; wall brown, 

 echinulate, pores 2. 



III. Telia similar to the uredinia but dark brown. 

 Teliospores ellipsoid or oblong-ellipsoid, 19-22 by 30-3 8/*, 

 rounded at both ends, slightly or not constricted at the septum ; 

 wall thin, uniform, finely verrucose, dark brown; pedicel 

 hyaline, slender, deciduous. 



On Taraxacum officinale Weber, Pictou, French River. 



According to Plowright two rusts are found on Taraxacum 

 in Europe, P. Taraxaci with only the uredinial and telial 

 stages and P. variabilis possessing an aecial stage as well. I 

 have found the present species so closely associated with aecia 



