(57) 
permitted, I should have been glad to submit this plant to the inspection of 
others before, perhaps, thus exposing my own incapacity. The only similar 
figure which I have seen is in Schleiden’s Principles of Scientific Botany, 
London, 1849, Plate 2, Fig. 8. This cannot be the plant. 
Of the four recorded United States species of Cystopus, three were 
found. These are exceedingly common on the plants indicated. They do 
not, however, have the blighting effect of the Peronosporice. Plants thor- 
oughly dotted with their pustules appeared to survive without great injury. 
Their microscopic character is so well known to botanists that nothing 
would have been gained by selecting new specimens to figure, so in my haste 
copies were selected as indicated. The other figures are from the collec- 
tion, but none of the plants are more common than these. 
Cystopus candiclus , Lev ., ( Plate 7, Figs. 1, 2, 3, 4.) Common on cru- 
ciferous plants, notably here on horse radish and cabbage. 
C. cubicus , Mart. On Ambrosia artemisise folia , the common rag weed. 
C. bliti, Bivon. On Portulaca oleracea (purslane) and Amaranthus 
retrojlexus. 
Perisporiacei. Notwithstanding the similarity of the names of these 
families, the plants are very different, as a glance at the plates will show. 
They, however, agree in their injuries to living plants, constituting very 
many of the leaf blights of this and other countries. Some of them are 
most exquisitely beautiful under the magnifier, a thing which the disciples 
of the development theory of species have not yet accounted for. Their 
beauty surely does not come from natural or sexual selection. The myce- 
lium runs over the surface of the leaves, never appearing to enter the cel- 
lular structure, yet, in some way, deriving nourishment from it. Here 
applications, as of sulphur, have direct effect. Here, too, the vine and the 
hop mildews belong. Conidia are borne in moniliform strings arising from 
the mycelium. The two together often give the affected leaves a dusty, 
whitened appearance, as if coated with whitewash. Later the spherical 
bodies — conceptacles — of dark color, as represented in the plates, are 
formed, sometimes exceedingly numerous, sometimes few and hard to find. 
The conceptacles have not yet been discovered in the vine disease of Europe. 
These conceptacles have at length radiating appendages , different from the 
mycelium, of many different forms, though constant within narrow limits in 
a given species. Inside the usually reticulated conceptacles there are 
attached to the base one or more sporangia or spore-sacks. These are thin 
and transparent, showing plainly the few or many spores. Sometimes, in- 
stead of sporangia , multitudes of naked and smaller spore-like forms are 
found ; and sometimes similar ones are contained in a stalked flask-shaped 
or urn-shaped vessel, as seen in Plate III, Fig. 7. Still other apparent 
fruit-bodies are found on the mycelium or the appendages of the conceptacles. 
I do not remember seeing these described, but have often met them and am 
fully convinced that they belong to the same plants. They are dark- 
colored like the Dematiei species, and of the forms shown in Plate III, Figs. 
2b, 2c, 2d, 7f, and Plate IV, Fig. 12. Save in quantity, they are not 
unlike forms of the black mildews found on thick-leaved plants and known 
