242 



Mycologia 



5. Peridermium minutum sp. nov. 



Pycnia solitary or few, or sometimes lacking, tawny to buck- 

 thorn brown, 0.2 to 0.4 mm. wide by 0.3 to 0.5 mm. long, averag- 

 ing 0.3 by 0.5 mm. 



Aecia scattered, usually in a single row on the outer side of the 

 leaves, low and inconspicuous, flattened laterally, 0.3 to 0.7 mm. 

 broad by 0.5 to 1.2 mm. long by 0.3 to 0.5 mm. high, averaging 

 0.5 by. 0.7 by 0.4 mm. ; peridia very delicate, rupturing longi- 

 tudinally with finely fimbriated edges which recurve on maturity ; 

 peridial cells ovoid, ellipsoid, or rhomboid in face view overlapping 

 but very little, if at all, 18 to 28 by 35 to 70 fx, averaging 21 by 

 48 /a, with walls 2 to 4 /x thick, the inner finely verrucose with 

 papillae ; aeciospores ovoid to ellipsoid to cylindric, sometimes 

 pointed at one end, 14 to 18 by 26 to 38 /x, averaging 15 by 33 ft, 

 with colorless walls 2 to 4 ft thick, the outer verrucose with blunt 

 tubercles 0.8 to 1.4 \l in diameter, 2.7 to 3.4 fx long. 



Peridermium minutum has been collected on Pinus glabra 

 Walt., and Pinus taeda only in Florida. 



The type specimen is F. P. 20768, collected by Hedgcock on 

 Pinus glabra near Gainesville, Fla., Mar. 15, 1916. 



In the study of various species of Peridermium it is found that 

 the pycnia possess good diagnostic characters, not heretofore rec- 

 ognized, and a key to the species known in the eastern United 

 States is in process of preparation in which these with other char- 

 acters will be used. 



It is also found that the peridial cells vary greatly in different 

 parts of the same peridium. Even when cells from the sides and 

 base of the peridium are twice as long as they are wide, the cells 

 at and near the top are only about half as large, with width and 

 length about equal and with walls much thickened. Since some 

 of the basal cells can practically always be found it seems better 

 to base the measurements on them alone. 



Office of Investigations in Forest Pathology, 

 Washington, D. C. 



