Natural History. 387 



face of llie contiguous country, it may be presumed to have 

 lieen the latter. The country is wholly of secondary formation. 

 Of the causes which enable animals of this class, which have 

 been suddenly enveloped in strata of earth, or otherwise shut 

 out from the air, without injury to the animal organ, to resume, 

 for a limited period, the functions of life on being restored to 

 the atmosphere, no explanation need here be given, as the 

 occurrence is a very common one, and is, perhaps, always more 

 or less the result of galvanic action. — Silliman''s Journal. 



6. On the Sensitive Plant, (Mimosa Pudica). By M. Dutrochef. 

 — It is known that the movements of the leaves of this plant 

 have their origin in certain enlargements situated at the articu- 

 lation of the leaflets with the petiole, and of the petiole with 

 the stem. Those only situated in the last articulation are of 

 sufficient size to be submitted to experiment. If, by a longi- 

 tudinal section, the lower half of this swelling be removed, 

 the petiole will remain depressed, having lost the power of 

 elevating itself ; if the superior half be removed the petiole 

 remains constantly elevated, having lost the power of depressing 

 itself. These experiments prove that the motions of the petiole 

 depend on the alternate turgescence of the upper and lower 

 half of the enlargement situated at the point of articulation, and 

 that contractibility is not the principle of these motions. 



If one part of the plant be irritated, the others soon bear 

 witness, by the successive falling of their leaves, that they 

 have successively felt the irritation. 'Ihus, if a leaflet be 

 burnt slightly by a lens, the interior movement which is 

 produced is propagated successively to the other leaflets of the 

 leaf, and thence to the other leaves on the same stalk. M. 

 Dutrochet found, 1. That this interior movement is trans- 

 mitted equally well, either ascending or descending. 2. That it 

 is also equally well transmitted, although a ring of bark be re- 

 moved. 3. That it is transmitted also, even though the bark and 

 the pith be removed, so that nothing remains to communicate 

 between the two parts of the skin, except the woody fibres and 

 vessels. 4. That it is transmitted also when the two parts 

 communicate only by a shred of bark. 5. That it is trans- 

 mitted when the communication is completed by the pith only. 

 6. But that it is not transmitted when the communication only 

 exists by the cortical parenchyma. It results from these 

 experiments that the interior movement, produced by irritation, 

 is propagated by the ligneous fibres and the vessels. The pro- 

 pagation is more rapid in the petioles than in the body of the 

 stem : in the first it moves through from -f^ to -j% of an inch in 

 a second, in the latter from -j^^ to -^W of an inch in the same 

 time. External temperature docs not appear to exert any 



