184 



Mycologia 



The plants of rusted Pyrola used in the experiments were 

 Pyrola americana Sweet and P. elliptica Nutt. 



While the experiment in the laboratory cannot be regarded as 

 conclusive owing to the scant infection and the remote possibility 

 of the cones having been infected before the trees were taken in 

 to the laboratory, yet the experiments in the field seem to the 

 writer to show beyond reasonable doubt that Peridermium con- 

 orum-Piceae is the aecial stage of Melampsoropsis Pyrolae. 



The poor infection in the laboratory experiments may have been 

 due to the fact that the tree was not in a flourishing condition or 

 that the provision made to keep the atmosphere moist about the 

 cones was not sufficient, or, as the writer believes, to the cones 

 not being old enough when the sowing was made. In the field 

 experiments the cones were more mature. It was also found that 

 Pucciniastrum minimum readily infected the cones of Tsuga when 

 they were so far developed that infection was regarded as 

 doubtful. 



In the region where the Pyrola rust was collected, the telio- 

 spores began to germinate about May 24. The pycnia of Per. 

 conorum-Piceae were noticed on the cones of Picea mariana in 

 the vicinity on July i, and the aecial spores were being shed on 

 July 16. The Peridermium was rather rare, only a cone or two 

 showing infection on the trees attacked, and in all only about two 

 dozen cones were collected, where they could be collected in 

 hundreds the preceding season. 



Pucciniastrum minimum (Schw.) Arthur 



During the summer of 19 10, in a small area that had previously 

 been swept by a fire, a very luxuriant growth of Rhodora canadense 

 (L.) BSP. resulted, and on the leaves of the Rhodora a splendid 

 development of the uredinia and telia of this rust was present. To 

 gain some clue to the aecial stage, leaves were gathered in early 

 spring and placed beneath small trees of Abies canadensis and 

 Tsuga canadensis and small trees of the same species were planted 

 among the rusted Rhodora. Trees of Picea grew near the 

 Rhodora, so these were not experimented with. It was thought 

 most probable that the aecial host was either Abies or Tsuga. 



Leaves with telia were also collected and the teliospores were 



