THE RUSTS OF NOVA SCOTIA. FRASER. 331 



distances make this view probable. Klebahn placed wads of 

 cotton batting in high exposed places and found thousands of 

 rust spores in these traps. He concludes that this is the most 

 probable method of rust distribution and accounts for the 

 reappearance in northern latitudes. Ericksson claims that the 

 grain seeds contain the rust in the form of "Mycoplasma," an 

 intimate mixture of the protoplasm of the fungus with that of 

 the host, and that under favourable conditions the mycoplasma 

 separates and developes the normal mycelium of the rust. This 

 would account for the reappearance of the rusts and the sudden 

 outbreaks. He claims to have found the "corpuscle" or first 

 visible signs of the "mycoplasm" separating from the normal 

 cell protoplasm, but Ward has shown these to be haustoria. 

 There is not sufficient evidence to support the theory, which 

 has received much attention owing to the valuable work done 

 by Eriksson in his study of the grain rusts. 



Rust Enemies. 



A parasitic fungus, Darluca filum Cast., is often present 

 on the uredinia or-telia. I have found it very common on all 

 the rusts infecting Juncus, and also on many of the sedge and 

 grass rusts. In some cases it was difficult to obtain teliospores 

 owing to its attack. I have also found it very plentiful on the 

 uredinia of Coleosporium Solidaginis and Phragmidium 

 Potentillae-canadensis. This parasite can be recognized by 

 the small, black pycnidia, which are filled with colourless, 

 fusiform two-celled spores. The pycnidia are usually on the 

 uredinia and occasionally on the telia and aecia. The parasite 

 is doubtless an important factor in checking the spread of rusts. 



Another parasite, a species of Tuberculina, was found 

 attacking the aecial stage of Gymnoconia inter stitialis, but it 

 did not seem to be generally distributed. 



The larvae of a species of Cecidomyia is very commonly 

 present feeding on the aeciospores of many species. These 



