THE RUSTS OF NOVA SCOTIA. FRASER. 349 



MELAMSORIDIUM Kieb. 



Uredinia with a firm peridium dehiscing by a central pore, 

 cells of the orifice sharp pointed. Urediniospores borne singly 

 on pedicels. Telia indehiscent, forming evident layers beneath 

 the epidermis. Teliospores oblong or prismatic, one-celled. 



The genus includes three species on Betulaceae. Arthur in 

 the North American Flora reports from North America only 

 the species described below. 



Melampsoridium betulinum (Pers.) Xleb. 

 Melampsoridium Betulae (Schum.) Arth. 

 & I. On Larix decidua Mill. (Europe). Not yet col- 

 lected in North America. 



II. Uredinia hypophyllous, on small yellow spots, 

 scattered, small, round, reddish-yellow, at length pulverulent; 

 peridium hemispherical, firm, opening by a central pore, cells 

 polygonal, with pointed cells at the orifice, points 10-14/* long. 

 Urediniospores elongate-elliptical or elongate-obovate, 10-16 by 

 25-40/u; wall colourless, thin, strongly and sparsely echinulate 

 except smooth apex. 



III. Telia hypophyllous, small, often thickly covering 

 the surface of the leaf, at first waxy yellow, becoming brown 

 and finally blackish, indehiscent. Teliospores prismatic in a 

 palisade like layer beneath the epidermis, 7-16 by 30-50/u, 

 somewhat rounded at each end; wall nearly colourless, thin, 

 slightly thicker at the apex, smooth. 



Uredinia and telia on Betula populifolia Marsh, B. lutea 

 Michx., Pictou. 



The uredinial stage of this species was common on Betula 

 populifolia about Pictou during the fall of 1909. It is con- 

 spicuous as the leaves are thickly covered with small yellow 

 spots and usually a number of leaves near together are infected. 



PROC. & TRANS. N. S. INST. Sci. VOL. XII. TKANS. 2 



