228 DEOSERA ROTUNDIFOLIA. CHAP. IX. 



become inflected, are not excited to further move- 

 ment by bits of meat placed on the glands, until 

 some considerable time has elapsed. It is generally 

 believed that with animals and plants these vapours 

 act by arresting oxidation. 



Exposure to carbonic acid for 2 hrs., and in one case 

 for only 45 m., likewise rendered the glands insensible 

 for a time to the powerful stimulus of raw meat. The 

 leaves, however, recovered their full powers, and did 

 not seem in the least injured, on being left in the 

 air for 24 or 48 hrs. We have seen in the third 

 chapter that the process of aggregation in leaves sub- 

 jected for two hours to this gas and then immersed in 

 a solution of the carbonate of ammonia is much re- 

 tarded, so that a considerable time elapses before the 

 protoplasm in the lower cells of the tentacles becomes 

 aggregated. In some cases, soon after the leaves were 

 removed from the gas and brought into the air, the 

 tentacles moved spontaneously ; this being due, I pre- 

 sume, to the excitement from the access of oxygen. 

 These inflected tentacles, however, could not be ex- 

 cited for some time afterwards to any further move- 

 ment by their glands being stimulated. With other 

 irritable plants it is known * that the exclusion of 

 oxygen prevents their moving, and arrests the move- 

 ments of the protoplasm within their cells, but this 

 arrest is a different phenomenon from the retardation 

 of the process of aggregation just alluded to. Whether 

 this latter fact ought to be attributed to the direct 

 action of the carbonic acid, or to the exclusion of 

 oxygen, I know not. 



Saohe, ' Traitc dc Bot.' 1874, pp. S4G, 1C37. 



