426 BULLETIN OF THE BUSSEY INSTITUTION. 
SYNOPSIS OF THE PERONOSPOREZ OF THE UNITED STATES. 
PERONOSPORA. 
Conrp1a solitary, borne on the tips of branching filaments, which 
pass through the stomata into the air. Odspores spherical, buried 
in the tissues of the foster-plant. 
PERONOSPORA INFESTANS (Mont.), Botrytis, Auct., De Bary, An- 
nales des Sciences, 4 Sér. Tom. XX., 1863. Potato-rot fungus. 
Mycelium slender, haustoria few, conidial-bearing hyphe irregularly 
swollen at intervals near the tip. Branches few, irregularly placed, 
conidia ovoid, apex papillate. Germination usually by means of z06- 
spores. Odspores (Artotrogus hydnosporus, Mont. fide Berkeley), dark 
brown, coarsely reticulated. Vide W. G. Smith, “ Quarterly Journal 
of Microscopic Science,” Oct. 1875. 
Common on potatoes in all the Atlantic and Middle States. In 
California, near San Francisco, May, 1875, Dr. H. W. Harkness. 
On tomatoes, Ravenel, South Carolina, September and October, 1859. 
PERONOSPORA NIVEA, UNGER. De Bary, l.c. No. 2. P. Um- 
belliferarum, Caspary, Monatsbericht, Berliner Akad. May, 1855. P. 
macrocarpa Ltabenh. Herb. Mycol. Mycelium torulose. Haustoria 
numerous, oval. Conidial-bearing hyphe, fasciculate, 3 to 7 from 
each stoma. Axis short, simple; branches few, short, at right angles 
to axis. Tips of ultimate branches loosely bi- or tri-partite. Conidia 
ellipsoidal, obtusely papillate. Germination by zodspores. Odspores 
rather large, numerous, epispore hyaline or slightly yellow. Plate II., 
Fig. 4, and Plate III., Figs. 9, 10. 
To this species we refer a fungus found by us twice, once at Cam- 
bridge, near Fresh Pond, on the under surface of the leaves of Gera- 
nium maculatum, L., in August, 1874, and again at Wood’s Hole, 
Mass., on the same plant, July, 1875.* It forms large pure white 
patches between the principal veins. There are two Peronospore 
found on species of Geranium in Europe, P. pusilla, Unger, and P. 
conglomerata, Fuckel. ‘The latter is very different from our species. 
The former, for a specimen of which, collected by Professor De 
* Since the above was sent to press, we have found the same species of 
Peronospora on a leaf of Geranium Lobertianum amongst the undetermined 
species of the Curtis Collection, No. 58, without date or locality. 
