

















THE POTATO-MOULD. 465 
each other; and while each has thought the other wrong, all 
have attained some approximation to the truth. 
The potato-mould is the Peronospora infestans Caspary, 
and were it not for its effects, would be regarded by every 
one of taste as a beautiful object. Were we flies or insects, 
_ which are so liberally endowed with sight and eyes, and 
i quite unconcerned about the crops, the leaves of the potatoes 
Would be quite a pretty set of objects to investigate, pre- 
_ senting handsome, white, many-branched and beaded-twigged 
- plants, with oval or egg-shaped seed-bodies on the tips of 
ich smaller branch. These vegetable growths issue from 
_ the breathing pores of the leaves, and besides feeding them- 
_ Selves on the nutriment intended for the leaves, choke up 
_ the internal and external passages and prevent the healthy ac- 
: tion from being maintained. Soon the leaves become at first 
- Paler, or yellow, then discolored spots appear, then the stems 
_ are spotted with dark patches. Even the cellular tissue (or 
pulpy part of the stems or stalks, “potato-stalks” as we call 
< them) is discolored and filled with dark clotted substances : 
Subsequently, sooner or later, the stalks putrify, the skin 
Separates from the harder or woody portions; next the 
tubers suffer, spots and decay appear in a more or less regu- 
: lar manner of concentric lines, the skin withers, a white 
_ Mouldiness often occurs, especially if the potatoes lie in a 
| Moist place; the “rot” increases with fearful rapidity, the 
has a disgusting odor, certain smaller insects help the 
_ Process at this stage, and putrescence closes the scene. 
A plant thus simple in its general structure, and capable 
$ "ng on its rapidly growing branches three thousand 
bro hundred and seventy (3,270) seed-like pods, each con- 
taining at least six seed-like bodies (zoöspores) on one square 
a of the under surface of the leaves, and from each 
ok in turn a perfect seed-bearing “mould” is produced 
eighteen hours, may be readily conceived to be capable, 
‘a as it is, of incalculable mischief. The reader may, 
“vet, calculate by reduction to fractions of an inch, the 
AMER, NATURALIST, VoL. Il. 

