BULLETIN OF THE BUSSEY INSTITUTION. 235 
what awl-shaped. The conidial spores are broadly oval, and very 
slightly papillate at the apex. When sown in water, the contents 
divide into a number of zoospores, from six to about twelve, which 
are discharged, swim about by means of two cilia, and finally come to 
rest, as in the manner already described in Peronospora viticola and 
other species. We have never found ripe odspores in the present 
species, and only once have we found young ones in the stalk of Jmpa- 
- tvens; although we have examined the cotyledons carefully, especially 
those which had fallen to the ground. As we have said, the fungus 
disappears very rapidly, and the fallen cotyledons, in which one would 
naturally look for odspores, are recognizable only for a few days. 
The species is apparently the same as that described by Schreeter, in 
“ Hedwigia,” September, 1877, found by him growing on /mpatiens 
noli-tangere, L., near Rastatt, Baden, in May, 1875. In no important 
respect does our plant differ from Schroeter’s description of the fungus 
to which he gives the name of Peronospora obducens. The species is 
evidently related to P. nivea, Ung., and P. viticola, B. & C. The 
haustoria remind one of the description of those of P. densa, Rab., 
given by De Bary. Some penetrate directly into the interior of the 
leaf-cells, while others simply form spherical depressions in them, and 
the “granule ” in the interior is very distinct in old specimens. The co- 
nidial stalks, while branching in a general way like those of P. viticola, 
are less dense, and more pyramidal in outline. 
At the same time that the fungus was found on Impatiens, a 
species of Peronospora was also gathered on young plants of Zv- 
patorium purpureum, but in very small quantities. The seedlings, 
which were not over four or five inches high, were gathered and 
placed in glass bottles under a bell-glass, to favor the growth of the 
Peronospora, but we were not successful in making the fungus 
appear on more than half-a-dozen leaves. ‘The species is interest- 
ing from the fact that it bears an exceedingly close resemblance to 
P. obducens, and may perhaps prove to be the same species. At any 
rate, it was not like any of the other species hitherto observed on Com- 
posite. ‘The mycelium was quite the same as that of P. obducens, but, 
owing to the denser structure of the Hupatorium leaf, did not show as 
distinctly. The conidial stalks were like those of P. obducens, and the 
spores were similar, but larger and rather broader at the base. No 
odspores were observed. Unfortunately, although several attempts 
