236 BULLETIN OF THE BUSSEY INSTITUTION. 
were made, we were not successful in making the conidia germinate, 
and we could not consequently attempt the inoculation of young Jmpa- 
tiens plants with the spores of the Peronospora on Hupatorium. With 
the imperfect material at our disposal, it is impossible to say precisely 
what the species is, whether new or not. From its form alone, we 
should think it only a variety of P. obducens, approaching P. nivea.* 
In the Twenty-eighth Report of the New York State Museum of 
Natural History, bearing the date April, 1876, is a species described 
by Mr. Peck under the name of Peronospora Geranii, on Geranium 
maculatum. It may be that this is the same species mentioned in the 
* Bulletin,” Vol. I. p. 426, and referred to P. nivea, Unger.; but as 
there is no mention made of the odspores, and as the branching of the 
conidial stalks is described simply as divaricate, we cannot venture to 
express any opinion. Mr. Peck states that the apices are not swollen, 
but considers the species related to P. gangliformis which could 
hardly be the case, as the apices of that species are markedly swollen, 
De Bary describing them in the following words: “ dichotomiz ultimz 
apice inflate in vesiculam tympaniformem, v. turbinatam y. subglo- 
bosam.” 
In the same Report, Mr. Peck mentions P. obligua, Cooke, as oc- 
curring on Rumex crispus, at North Greenbush, N.Y. We are much 
indebted to the politeness of Mr. Peck for specimens of the New 
York plant, and also to Mr. M. C. Cooke, who kindly communicated 
English specimens; and we have been able to recognize the species as 
one which we have found, from May to November, on leaves of Rumex 
ecrispus at Newton, and also in August on leaves of &. obtusifolius at 
Brewster, Mass. We have carefully examined fresh specimens of the 
fungus, which was allowed to develop under glass in the laboratory, 
that the spores might be seen both when young and old and we are 
compelled to differ from the opinion held by the above-named gentle- 
men, and consider that the species is not a true Peronospora, but a 
Ramularia. The mycelium of the fungus is found in all parts of the 
leaf, but especially in the round dark spots recognized by the naked 
eye. It is very small, .002 mm. in diameter without haustoria, and is 
quite unlike the mycelium of a Peronospora. The mycelium makes 
its way through the stomata into the air, a large number of threads 
* Since the above was sent to press, Peronospora Cyparissie, De Bary, was 
found on leaves of a Euphorbia collected by Mr. J. B. Ellis, Newfield, N. J. 
