Irritability

Irritability in Plants, a term employed to designate phenomena very interesting and curious, but than which none connected with vegetable life are more imperfectly understood. Such are the phenomena of what is usually called the Sleep (q.v.) of plants; the motion of the spores of many cryptogamic plants by means of cilia; the motions of some of the lowest Algae; those caused by agitation or by the touch of a foreign body in the leaves of Sensitive Plants (q.v.); the motions of Insectivorous Plants (q.v.), &c.