204 Irritability. 



for six or eight day3, and continue to vegetate as if in the earth. 

 A plant was put in a solution of nux vomica at nine in the morn- 

 ing ; at ten o'clock the plant seemed unhealthy ; at one the petals 

 were all bent in the middle; and in the evening the plant was 

 dead. Ten grains of an extract of cocculus suberosus, dissolved 

 in two ounces of water, destroyed a bean plant in twenty-four 

 hours ; prussic acid produced death in twelve hours ; laurel 

 water in six or seven hours ; a solution of belladonna in four 

 days ; alcohol in twelve hours. From the whole of these expe- 

 riments, M. Marcet concludes — 1st, That metallic poisons act 

 upon vegetables nearly as they do upon animals ; they appear to 

 be absorbed and carried into the different parts of a plant, altering 

 and destroying the vessels by their corrosive powers. 2dly, That 

 vegetable poisons, especially those which have been proved to 

 destroy animals by their action on the nervous system, also 

 cause the death of plants; whence he infers that there exists in 

 the latter a system of organs which is affected by poisons nearly 

 as the nervous system of animals. These facts have been con- 

 firmed by other experiments of M. Macaire. Irritability, in the 

 common acceptation of the term in botany, means those extreme 

 cases of exeftability in which an organ exhibits movements alto- 

 gether different from those we commonly meet with in plants. 

 Of this kind there are three distinct classes, namely, those which 

 depend upon atmospheric phenomena, spontaneous motions, and 

 such as are caused by the touch of other bodies. Among the 

 cases of irritability excited by particular states of the atmosphere, 

 the singular phenomenon called by Linnaeus the sleep of plants, 

 is the most remarkable. In plants with compound leaves, the 

 leaflets fold together, while the petiole is recurved at the approach 

 of night; and the leaflets again expand and raise themselves at 

 the return of day. In others, the leaves converge over the 

 flowers as if to shelter those more delicate organs from the chill 

 air of night. The flowers of the crocus and similar plants ex- 

 pand beneath the bright beams of the sun, but close as soon as 

 they are withdrawn. The CEnotherecs unfold their blossoms to 

 the dews of evening, and wither away at the approach of day. 

 Some Silenes roll up their petals in the day, and expand them at 

 night The florets of numerous compositse and the petals of the 

 genus Mesembryanthemum, are erect in the absence of the sun, 

 but become reflexed when acted upon by his beams ; and many 



