Potato

3806

Potential

potassium chloride from Slassfurt with the
sodium nitrate of the Peruvian deposits. Po-
tassium chlorate, KCIOs, i^ obtained by the
action of excess of chlorine on a hoi solution
of caustic potash (i'>K011+.*CL=5KCl+
KClOn+sHjO), or indirectly through the cor-
responding calcium compound prepared in a
similar way. Pofussiinn cyanide, for which the
sodium compound is no\v largely substituted,
is a white fusible salt that is soluble in water
and is intensely poisonous. PotusMinii chlor-
ide, KC1, known commercially as Muriate oj
Potash, closely resembles common salt, and
has been largely obtained from the deposits at
Stassfurt.

Politic

1." Potato plant—leaves, roots, under-
ground stems with tutors showing 'eyas';
2. flower, Emotion; 3. fruit, Motion; 4. unc-
tion of l«if, greatly onfarigxi, showing the
fungus Phj/tovfUhara infatarw, which givea
rise to Into blight

Potato, the edible farinaceous tuber of a
native American perennial (Solatium tuberos-
wn), one of the most widely cultivated of ag-
ricultural plants, and next to the principal
cereals the most valuable as a source of human

food. It came originally from South America;
was introduced into North America and Eu-
rope in the r6th century; and by the latter
half of the jSth was recognized as a staple
crop in the temperate regions of both conti-
nents. The potato thrives best in a rich, sandy
loam abundantly supplied with organic mat-
ter, and naturally well drained. Potatoes are
grown primarily as a food crop, but are of
importance as a source of starch, especially for
sizing paper and textiles. They are used also
. s a source of industrial alcohol in Europe, as
a stock food, and in the manufacture of potato
flour and glucose. The potato is subject to a
number of diseases, some of which are at times
the cause of serious loss. Early Blight or Po-
tato Leaf Blight is a widespread and destruc-
tive disease due to the fungus Altcrnaria solani.

Lute Blight, known also as Potato Disease
and Potato Blight, is especially prevalent in
damp, dull weather and in moist or wet soil.
It is due to the lurwusPhyiophthorainfestans,
and is much more destructive in European
countries than in America. Wilt or Brown Rot,
especially troublesome in the southern United
States, is caused by the Rafittiis solaiiaccaruiu,
and may be recognized by the sudden wiltinp
of the vines and the browning of the vascular
bundles in the tubers, followed by rotting,
Potato Scab is due to a soil fungus, Qospora
scabies, which causes rough irregular blotches
on the tubers sometimes covering the entire
surface- The most serious insect pest of the
potato is the Colorado Potato Beetle, or Po-
tota Bug (Leptinotarsd decemlineata), a leaf-
eating insect native to the Rocky Mountain
region, whence it has spread eastward to the
Atlantic Ocean. Another serious insect pest
is the Flea Beetle (Rpitrix rucumeris), a tiny
black insect, about one-sixteenth of an inch in
length, which feeds upon the leaves of the
young plants.

Potemkin, Gregory AlexandrovitcH,
Prince (1749-91), Russian statesman, mem-
ber of a Polish family, was born near Smo-
lensk. During the short reign of Peter m. he
rind the Orloffs plotted with Peter's wife, Cath-
erine, to bring about the adbication of the
Tsar and the accession of Catherine. In 1776
he became the acknowledged favorite of the
Tsaritsa and from that time till his death he
guided the foreign policy of Russia.

Potential, a function of fundamental im-
portance in the theory of attractions, and also,
by a mathematical extension of meaning, in
hydrodynamics. It is a function of the posi-
tion of a point, its value depending upon the
attracting matter which acts upon unit mass