Fraser: Cultures of Heteroecious Rusts 191 



first weeks of July. These aecia appeared to be connected with 

 Uredinopsis mirabilis on Onoclea sensibilis. A second crop ap- 

 peared about the first of August and lasted during the month. 

 These seemed to be connected with Uredinopsis Osmundae and 

 U. Phegopteridis. There was a striking difiference between the 

 field appearance of the earlier and later aecia, and the spores of 

 the former averaged about 8/x smaller than the latter. 



The writer is convinced that at least two forms are confused 

 under Peridermium balsameuin and that these are connected with 

 Uredinopsis on ferns. It may be that one is also the aecial stage 

 of Pucciniastrum arcticiim on Rubus. There was considerable 

 field evidence to support this view, but that does not seem 

 probable. Preparations have been made to carry on further 

 experiments next year, and the writer looks forward with confi- 

 dence to throwing some light on the life history of the fern rusts 

 so little understood at present. 



Attempts were made to germinate the urediniospores of Ure- 

 dinopsis mirabilis and with some success. Germ tubes emerged 

 from germ pores, two placed near the beak and two near the 

 base of the spore. The germ tube was that of the usual uredo- 

 spore but very small. Two germ tubes only emerged from each 

 spore on germination usually, one from the oppositely placed 

 pores either at the apex or base, but sometimes both on the same 

 side of the spore. Attempts were made to infect plants of Ono- 

 clea sensibilis with uredospores and the experiments were suc- 

 cessful but opportunity was not given to follow the experiments 

 carefully. The experiments indicated, however, that the first 

 spore to appear in the fern rust is the uredospore and that it is 

 functionally a uredospore. 



Pucciniastrum agrimoniae (Schw.) Tranz 



There was a very rich development of both the teHal and ure- 

 dinial stages of this rust on Agrimonia gryposepala Wallr. near 

 New Glasgow for several years, but no clue to the aecial stage 

 was noticed. All the conifers of the region grew among the rust 

 except Tsuga canadensis. Repeated attempts were made to ger- 

 minate teliosporic material from this place but without success. 

 Leaves of the host were suspended above young trees of Tsuga 



