314 THE RUSTS OF NOVA SCOTIA. FRASER. 



Agrimoniae, Puccinia coronata is described in the following- 

 pages as Puccinia Lolii and Puccinia rubi$o-vera as Puccinia 

 triticina. Peridermium decolorans is the aecial stage of 

 Melampsoropsis ledicola and Peridermium elatinum of 

 Melampsorella elatina. The position of Gymnosporangium 

 Juniperi and Rostelia lacerata is discussed under the genus 

 Gymnosporangium. 



In the present paper 92 species and 2 forms are described. 

 A few of these have not been previously reported from North 

 A-inerica. 



In the general discussion and in some of the notes I am 

 indebted to the literature of the rusts. A list of the works 

 consulted will be found at the end of the paper. 



INTRODUCTION. 



The Uredinales (Uredineae) constitute a large group of 

 fungi which are parasitic on flowering plants and ferns. Their 

 structure consists of an inconspicious mycelium in the tissues 

 of the host plant and more or less conspicious spores that 

 usually break through the epidermis and appear as powdery 

 masses or crusts. The vegetative mycelium is similar through- 

 out the group, but the spores produced are unlike so that a 

 study of the rusts is largely a study of the spore forms and 

 their relation ; to each other and to the host plants. The 

 mycelium eventually gives rise to the teliospores which are 

 generally regarded as the last stage. Spores of five kinds are 

 produced, though they are not all present in every species. 

 Arthur has proposed new terms for these spores, which are 

 used throughout this paper. The list below gives in order the 

 term proposed by Arthur and the more commonly used term 

 for each spore form: 



Basidiospore, sporidium. 



Pycniospore, spermatium . 



Aeciospore, aecidiospore. 



Urediniospore, uredospore. 



Teliospore, teleutospore. 



