THE RUSTS OF NOVA SCOTIA. ERASER. 347 



Melampsora Medusae Thuem. 



0. Pycnia amphigenous, mostly hypophyllous. 



1. Aecia hypophyllous, often on the young twigs causing 

 deformation, elongate or rounded, ruptured epidermis incon- 

 spicuous, pale yellow fading to white. Aeciospores globoitl, 

 ahout 16-20/x; wall colourless, thick, minutely verrucose. 



II. Uredinia amphigenous or mostly hypophyllous, often 

 on yellowish spots, scattered, roundish, very small, soon naked, 

 somewhat pulverulent, orange-yellow, fading to pale yellow. 

 Urediniospores ellipsoid or obovate-ellipsoid, 16-17 by 22-27^, 

 wall colourless, rather thick, sparsely but rather strongly 

 verrucose; paraphyses numerous, capitate, thick walled, inter- 

 mixed with the spores. (Urediniospores often flattened later- 

 ally with flattened sides smooth). 



III. Telia amphigenous, usually only hypophyllous, 

 scattered or confluent, irregularly roundish, small, slightly 

 elevated, reddish-brown, becoming dark chocolate-brown, 

 subepi dermal. Teliospores prismatic, 10-16 by 27-46/*; wall 

 smooth, light brown, uniformly thin. 



Pycnia and aecia on leaves and cones of Tsuga canadetisis 

 (L.) Carr., Pictou, Truro. 



Uredinia and telia on Populus grandidentata Michx., Pic- 

 tou, New Glasgow, Truro; P. tremuloides Michx., Pictou. 



The writer has shown by cultures that this species has in 

 this region its aecia on Tsuga-candensis. (See Mycologia 4: 188. 



1912). The aecial stage 

 is Caeoma Abietis-caiwdensis 

 FarL, which is rather com- 

 mon on its host. Arthur 

 has shown by cultures that 



2. Surface view of part of teliuui of the aecial Stage also OCCUl'S 

 Melampsora Medusae. Side view. Qn j^^ (J()Ur Mycol 1Q . 



13. 11)04: 11:52. 1905; 12:13. 1906). It is probable that 

 there are two races of the same species, that in the east having 

 aecia on Tsuga and in the west on Larix. 



