IX THE MOTOR ORGANS OF LEAVES. 



31 



shown by the continuous discharge which accompanied free supply of water. A 



striking illustration is also afforded of tho dependence of turgidity not only on 

 intrinsic, but also on extrinsic conditions; not only on osmotic capacity of the cell- 

 sap, but on conditions of general loss and supply of water. It cannot bo supposed 

 that any appreciable increase in osmotic property of tho tissues occurred between the 

 14th and loth March, and yet a very considerable rise in tumescence t«>ok place 

 then, coincident with renewed free supply of water. 



The contrast between the results in cases of this kind and those presenting 

 themselves where death of the tissue is determined by means which do not intro- 



duce permanent artificial osmotic properties into it, comes out very dearly on com- 

 paring the above figures with those furnished by an experiment on the results follow- 

 ing immersion in an alcoholic solution of corrosive sublimate: 



Date. Weight. Loss. Percentage loss. 



December 21st ... 29'22 



• . • • • • 



99 



99 



99 



35 



9J 



» 



22nd ... 26-44 278 95 



23rd ... 24-68 4'54 155 



24th ... 22-92 6-30 215 



25th ... 21-82 740 24*2 



27th ... 21-03 8-19 28-0 



30th ... 20-50 8-72 298 



Even here, however, the initial loss of fluid and turgescence is not so great as 

 in cases where the functional activity of the tissue is abolished by means of extremes 

 of temperature, vapour of chloroform, or other conditions in which no appreciable 

 addition of extraneous materials to the cell-sap is involved. The peculiarity of the 

 phenomenon of artificial maintenance of turgescence by means of ammonia lies in its 

 persistent character. In cases of poisoning by alcoholic vapour under conditions of free 

 water-supply, the loss of fluid and of turgescence during the first twenty-four hours 

 is relatively limited, and may even fall as low as it is where ammonia is the toxic 

 ao-ent, but there is no permanent arrest established, and the loss, although retarded in 

 the outset, goes on steadily progressing. Exposure to an atmosphere of ammonia is 

 followed almost immediately by a certain amount of discharge of fluid and con- 

 spicuous change of colour in the tissues, the abolition of functional activity being 

 apparently much more rapid than where chloroform is employed ; but, because the 

 ammonia is readily absorbed by the cell-sap and imparts certain properties to it t the 

 loss of turgescence connected with the cessation of the normal manufacture of 

 osmotic materials is very soon arrested, whilst chloroform (acting purely in arresting 

 functional activity) does nothing to prevent the elastic recoil of the cell-walls from exert- 

 ing its full effect. 



The effects of ammonia in artificially maintaining turgescence are specially 

 conspicuous and measurable in dealing with succulent tissues such as those of Falanchoe, 

 but they also come out very clearly in many other cases, such as those of the two 

 following experiments: 



Experiment XXI. — Two fully expanded flowers of scarlet Hibiscus were taken and 

 the extremities of their stalks were freshly divided under the water of the vessels in 



