1921] ADAMS—BLISTER RUSTS 137 
does not have to be depended upon. The presence of pycnia is 
best determined by carefully removing the overlying bark from 
the cortex. The pycnia develop in the subcorticular tissue. Free- 
hand sections can easily be cut and mounted with a little dilute 
alcoholic eosin which provides a satisfactory means for examina- 
tion. The pycniophores of P. Comptoniae are shorter and more 
uniform in diameter throughout their length than those of P. cere- 
brum (figs. 1-4). It is found that the pycniophores are longer and 
more tapering with P. cerebrum. No conspicuous difference in size 
could be found between the pycniospores of the two species. The 
following measurements for comparison are taken from killed 
material and stained with Fleming’s Triple. The length of the 
pycniophores was taken from the sub-basal cell to the tip, and for 
Peridermium Comptoniae was 15-27 mb; while for Peridermium cere- 
brum it was 30-36 uw. A comparison of the pycniophores in these 
two species is shown in figs. 1 and 3, drawn at the same magni- 
fication. 
STATE COLLEGE, Pa. 
LITERATURE CITED 
1. Apams, J. F., Rusts on conifers in Pennsylvania. Penn. State Coll. Agric. 
Exp. Sta. Bull. 160. 1919. 
2. bie J. S., Pycnia of Cronartium pyriforme. Phytopath. 6: 446-447. 
16. 
ii paiaebe G. P., Rep. Sta. Bot. Conn. Agric. Exp. Sta. Bull. 214. rorg. 
- sAstificial infection of Ribes species and white with Cro- 
poe ribicola. Amer. Plant Pest Committee Bull. 2. 1-15. rgr9. 
5. Dones, B. O., and Apams, J. F., Some observations on the as of 
Peridermium iersivnnn. Mem. Torr. Bot. Club 17: 253-261. 1918. 
6. Hepccock, G. C., BETHEL, E., and Hunt, N. R., Notes on some western 
Uredineae. Abst. Phyt. 8:73. 1918. 
7. Hepecock, G. C., and Lone, W. H., Identity of Peridermium fusiforme 
with Paidvnian cerebrum. Jour. Agric. Res. 2:247-249. 1914. 
8. Surat, M., On the genetic connection between Peridermium giganteum 
(Mayr.) Tubeuf and Cronartium quercuum (Cooke) Miyabe. Bot. Mag. 
Tokyo 13:74~79. 1890. 
9- Werr, J. R., and Husert, E. E., Pycnial stages of important forest tree 
rusts. Phytopath. 7:135-139. 1917. 
