No. 15 in a Series of 253,486.

POISON IVY (Toxicodendron). The American poison ivy is one of our chief sources of justifiable national pride. Europe may have history and culture, but America has mere plants that strike terror into the heart of the bravest.

For European readers, it is necessary to explain that poison ivy is a variable North American plant, either vining or standing upright (when it is known as “poison oak”), the mere touch of which is enough to produce painful lesions on the skin. The legendary toughness of rural Americans can be attributed largely to repeated outbreaks of poison ivy, which eventually turn the skin into a leathery armor impervious to any ordinary pain.

The necessity of avoiding poison ivy has given rise to a number of well-known folk rhymes, many of which are charming in their rural simplicity:

“Leaflets three,
Let it be.”

“Hairy vine,
No friend of mine.”

“Leaflets ovate to rhombic, mostly acuminate,
’Twould be best for bovines not to ruminate.”

“Tardily deciduous pubescence beneath
Makes an itchy Christmas wreath.”

“A woody vine bearing glabrous berries of creamy white is
A sure precursor of urishiol-induced contact dermatitis.”

Poison ivy is governed by the planet Mars, where it grows in a particularly luxuriant manner and is an important cash crop.