114 
Mycologia 
in such cases, careful microscopic diagnoses must be held im- 
portant. 
Key to the Foliicolous Species of Peridermium on Pinus, all being 
the Aecial Stage of Species of Coleosporium 
Peridia low, fragile, and inconspicuous. 
Peridial cells quadrilateral in face view, 20-29 /x 
long. 
Peridial cells oblong in face view, 38-55 /x long. 
Peridia medium-sized, mostly 0.5-1 .2 mm. high. 
Peridial cells slightly overlapping, the side walls 
3-4 /x thick or less. 
Spores broadly ellipsoid, the wall 2/1 or less 
thick. 
Spores narrowly oblong, the wall 2/1 or more 
thick. 
Peridial cells strongly overlapping, the side walls 
5-9 fx thick. 
Spores moderately and uniformly verrucose, 
the wall uniformly thick. 
Spores closely verrucose, sometimes with a 
smooth area, the wall varying in thickness. 
Peridia large and firm, mostly 0.7-1. 5 mm. high, occa- 
sionally up to 2.5 mm. 
Peridial cells rather finely verrucose, spores ver- 
rucose with large deciduous papillae. 
Peridial cells rather coarsely verrucose. 
Peridial cells with side walls moderately thick 
( 4-7 #*)• 
Spores evenly and moderately verrucose. 
Spores densely verrucose with prominent 
elongate papillae. 
Peridial cells with side walls very thick 
(7-1 2fx). 
Spores with walls moderately thick 
(2.5-3 . 5 m ). 
Spores with walls thick (3. 5-5. 5 fx). 
1. P. delicatulum. 
2. P. inconspicuum. 
3. P. Fischeri. 
4. P. montanum. 
5. P. calif ornicum. 
6. P. acicolum. 
7. P. gracile. 
8. P. intermedium. 
9. P. Rostrupi. 
10. P. guatemalense. 
11. P. carneum. 
i. Peridermium delicatulum Arth. & Kern, Bull. Torrey Club 
33 : 412. 1906 
0. Pycnia 0.3-0.4 mm. broad by 0.5-1 mm. long, low-conoidal, 
80-100 fx high. 
1. Aecia erumpent from longitudinal slits 1-5 mm. long, delicate, 
scarcely protruding above the ruptured epidermis ; peridial cells 
usually quadrilateral or hexagonal in face view, 16-24x20-29 /x , 
not or only slightly overlapping, the side walls 2-3 thick, the 
inner wall finely and closely verrucose with uniform papillae; 
