352 BOTANICAL GAZETTE [May 
disturbing element which prevents our seeing just what would happen if 
the carbon dioxide were the only diffusing gas in the question; it is 
a case where the membrane permits some of the solute to escape. 
The fact that carbon dioxide diffuses more rapidly through a 
cuticle if the latter is kept moist, shows that water also can pass through 
it, and, therefore, that in the case of a solute which cannot permeate 
it, the cuticle would serve as the semi-permeable membrane of an 
osmometer. I have set one up, using a leaf of Farfugum as the mem- 
brane, and 20 per cent. NaCl as the solution inside. It was a week 
before any endosmosis was apparent, and in three weeks the column 
rose barely 6™". I believe that though this cuticle be absolutely 
impermeable for the salt, such a resistance as it opposes to the water 
must prevent its use for the accurate measurement of osmosis.—EDWIN 
BINGHAM COPELAND, University of West Virginia, Morgantown. 
A NEW SPECIES OF PUCCINIA. 
Puccinia Thompsonii, n. sp.—III. Epiphyllous or occasionally 
amphigenous. Sori scattered, oblong to linear-oblong, 0.2 5—6™™ long, 
reddish to chestnut-brown, erumpent, the ruptured epidermis flanking 
the sides. Spores oblong-clavate, constricted at the septum; vertex 
rounded or sometimes obtusely pointed, thickened; base obtusely 
rounded; epispore rather thin, very smooth, color golden-brown OF 
lighter, 48-68 X 15-24. Pedicel slender, hyaline, 1.5-2.5 times the 
length of the spore. 
On Carex stenolepis Torr. (C. Frankii Kunth). Lebanon, Ind., 
Mar. 19, 1891, J. C. Arthur; Pine Lawn (St. Louis), Mo., spring of 
1894, C. H. Thompson; Alexandria, Ind., Sept. 23, 1898, AZéss Lillian 
Snyder; Greencastle, Ind., Oct. 1898, ZL. M@. Underwood; Pine Lawn 
(St. Louis), Mo., Jan. 2, 1899, Hume & Thompson. 
This species somewhat resembles P. Bolleyana Sacc., but differs 
from it in the more scattered, larger, oblong, lighter-colored sori and 
the somewhat longer and narrower spores. The epispore of the upper 
cell is not quite so much thickened. The species is named for C. H. 
Thompson, of the Missouri Botanical Garden, who first called nce | 
attention to it. In the above description the material from St. Louis 
is taken as the type, as its abundance has furnished ample material 
for study. However, the material collected at the several points 1? 
Indiana, above cited, shows no appreciable variation. Iam indebted 
