Platk VII. 
Fiffs. 1 and 2, Peridertnium cerebrum on Ijodge Pole pine. (Figr. 1, longfitudinal section of 
branch.) (Fig:. 2, view showing- sori broken open exposing spores.) 
Fir. Peridermium elatinum on Abies subalpina. Photograph by Charlotte M. King. 
