118 IRRITABILITY. 



peculiar motion seen in Hedysarum gyrans, which is not 

 occasioned by any touch or movement of the air, as in 

 Mimosa, Oxalis, Dionsea, etc. ; no sooner, says Linnaeus, 

 had this plant acquired its ternate leaves, than they 

 began to be in motion in every direction ; this move- 

 ment did not cease during the whole course of their ve- 

 getation ; nor were they observant of any order, time, or 

 direction, one leaflet frequently revolved whilst the 

 other on the same petiole was quiescent ; sometimes a 

 few leaflets only were in motion, then almost all of 

 them would be in movement at once ; the whole plant 

 was very seldom agitated, and that only during the first 

 year. It continued to move in the stove during the se- 

 cond year of its growth, and was not at rest even in the 

 winter. The irritability of this plant, says Burnett, is 

 never so great even in our best hot-houses as it is said 

 to be in its native climate, and its motions are very sel- 

 dom so lively as those described by Linnaeus ; warmth 

 appears essential, for they are always most observable 

 when the heat is greatest. That they are not attribu- 

 table to the sun's rays, or to any currents of air, is 

 shown from the fact that the plant loves the shade, and 

 that the motion is most evident when the stove is 

 closed, and the atmosphere quite still. 



171. Not a few instances are to be met with in the 

 lowest tribe of plants, as in certain Algse, in which mo- 

 tion decidedly spontaneous is to be seen, and which 

 has given rise to doubts as to whether these beings 

 were really plants or animals, and which, accompanied as 

 they are by other phenomena which hold no analogy to 

 what is seen in the higher orders of either kingdoms, 

 have rendered the exact situation of them in the scale 

 of created objects a doubtful point, at least with those 

 who would place definite limits between the animal and 

 vegetable kingdoms ; these, however, we shall pass 

 over, and notice another subject. 



172. When speaking of germination and the evolu- 

 tion of the radicle and plumula, we remarked the gene- 

 ral and powerful tendency of the former to direct itself 



