LIFE OF PLANTS. 251 



ring on the opening of* the water-bladder, with numerous 

 rib-shaped processes, to which we might ascribe a function 

 similar to that of the elastic ring of the capsules of the 

 Ferns. 



Finally, the alternate approximation and separation of the 

 cilia in the setting of the orifice of the Mosses, is a j)urely 

 hygroscopic phenomenon, since every change in the quantity 

 of vapour contained in the atmosphere sets this alternation 

 a-going. 



379. 



But what, without doubt, are automatic motions, or such 

 as vve cannot account for by mechanical causes, but by higher 

 powers, are, in the first place, the movements of fresh-water 

 Oscillatoria? during their growth. By the microscope, we 

 observe these motions under the influence of sunshine so 

 striking during the rapid increase of the bodies, that we can 

 scarcely refrain from supposing, that we perceive a trace of 

 animal life, or from considering these bodies as holding a 

 middle place in the two organic kingdoms. Equally striking 

 are the movements of the Hedysarum gyrans during its ra- 

 pid growth. It is the smaller side leaves, however, which 

 incessantly exhibit this circumvolving motion. Even the 

 power of detaining flies which belongs to the Dlouaa musci- 

 pula^ may be ascribed, notwithstanding the wonderful mecha- 

 nical means for producing it, to the irritability which, from 

 other proofs, we know to belong to the leaves of that plant. 



The collapsing of the leaves of what are called Sensitive 

 Plants, which belong to the species Mimosa, Schrankia, 

 ^schynomene, Averrhoa, Oxalis, and Smithia, is, notwith- 

 standing all earlier attempts to explain it mechanically, an in- 

 dubitable consequence of irritability ; and this is the more evi- 

 dent that in one of them, the Averrhoa Caramhola, it is not 

 the leaves which were touched, but those placed opiK)site to 

 them, whicli collapse and fall down. 



