320 THE RUSTS OF NOVA SCOTIA. FKASER. 



The urediniospore is primarily a spore for the rapid dis- 

 tribution of the fungus so that it may repeat, that is the 

 nredospores may infect the host plant. Often the first formed 

 generation which appears in early spring and originates either 

 from basidiospore infection, aeciospores, or from perennial 

 mycelium, are called ''primary" uredinia, and the second 

 generation which develops from uredospore infection are called 

 ^secondary" uredinia. The primary uredinia are usually 

 larger and more richly coloured, as in Puccinia obtegens. 



In countries where the aecial host is absent and the 

 urediniospore propagates the fungus, there is a tendency to 

 abundant development of this stage, as in Puccinia graminis in 

 Australia. This rust has lost the power to infect the barberry 

 there and urediniospores are produced abundantly, almost to 

 the exclusion of the tcliospores. 



Urediniospores retain their germinating power for some 

 time. Bolley states that the uredospores of P. graminis in 

 certain cases may survive the winter even in North Dakota, 

 and thus carry the fungus over that period. 



Amphisp ores. 



.Another kind of urediniospore which has thickened walls 

 and persistent or subpersistent pedicels is found in some species 

 of gramineous rusts. The sori resemble telia and the spores 

 have been mistaken by some observers for teliospores. They 

 can be separated from the true teliospores by the presence of 

 several germ-pores. They have been germinated in 1901 by 

 Oarleton and later by Arthur, and the germ tube of the 

 nrediniospore was the result. They have not been found in 

 any species represented in Nova Scotia. 



Arthur states that they belong to species having their main 

 development in arid or semi-arid regions. They occur only in 

 the United States and Mexico, except one species in India. 

 Arthur (Bull. Torr. Bot. Club 32: 35. 1905) gives a list of five 

 species which he found to possess amphispores. All are from 



