36 



THE CAUSES OF FLUCTUATIONS IN TUKGESCENCE 





fluctuations in the rate of their manufacture are at once followed by conspicuous alter- 

 ations in tint and texture. In a certain number of cases, however, they are stable, and 

 here an entire cessation of protoplasmic activity may occur without giving rise to any 

 appreciable results. In the first instance, death gives rise to immediate alterations in colour 

 and turgescence ; in the latter, it produces no appreciable effect. Turgescence is normally 

 solely dependent on certain properties of the cell-sap; and, so long as these are retained, it 

 is a matter of indifference whether living protoplasm be present or not, or what changes 

 in form it may undergo. In so far as intrinsic conditions are concerned, it is loss of 

 osmotic properties in the cell-sap, and not any direct alteration in the structure of the 

 protoplasm, that gives rise to loss of turgescence: but, in dealing with any experiments 

 on tissues in which the maintenance of turgescence is normally related to continued 

 vitality, we have carefully to bear in mind that certain extrinsic conditions may come 

 in to modify the nature of the results accompanying a cessation of functional activity. 



In cases where the cessation of functional manufacture of osmotic products is accom- 

 panied by the introduction of extrinsic products (as in experiments where the leaves of 

 Kalamhoe or the flowers of Hibiscus are exposed to an atmosphere of ammonia), the loss 

 of turgescence attending the death of the tissues is reduced to a minimum ; whilst, in 

 cases where no such modifying influence is present, the amount of loss will be determined 

 solely by the extent to which any stable osmotic materials of intrinsic origin are present. 

 In all such experiments we have to consider the influence of the conditions to which the 



■ 



tissues are exposed in producing the following effects : 



/ 



ls^— Cessation of functional activity. 



2nd— Addition of extraneous osmotic constituents to the cell-sap. 

 3rd— Disturbances in the relations of supply and evaporative loss of fluid 



m 



Alterations in the filtrative power of the protoplasm, and possibly of the 



cell-walls. 



In cases where leaves such as those of Kalanchoe 



Hibiscus rosa- sinensis, are 



? 



posed to an atmosphere of ammonia 



or flowers such as those of 



ith the bases of their stalks subaqueously divided and immersed in water 



moist chamber, and 



find turg< 



remaining almost unaffected by the death of the tissues, because of the addition of 



extraneous osmotic materials to the cell-sap 



ova[ 



loss of fluid. Where similar 



form under otherwise like conditions 



abolition of turg 



functional activity, because the freest supply and abolished evaporative loss of 



not make up for the loss of osmotic propertie 



recoil of the cell 



xisting with free supply and abolished 



posed to an atmosphere of chloro- 



follows the cessation of 



water will 

 sting the elastic 



in the cell-sap 



Where, as in experiment XXI of chapter II, the same tissues 



j , , »■'■. \ \ wwpier 11, tne same tissues are 



exposed to an atmosphere of ammonia, without special provisions for securing supply and 

 abolishing evaporative loss of water ' 1 " - r J 



spite of the addition of extraneous osmotic materials to the cell-sap 

 they are e: a ._.»..-. r 



very considerable loss of turgescence takes pi 



and finally, where 



, ! V * f S t i ?• T^ TT ^^ the l0SS * ^^ence associated with 

 abolition of functional^ activity is retarded, apparently owing to the introduction of obstacles 



«*,rf fr Wh *i • * i *• W ^ ar «>st the loss of turgescence; they merely 



retard it, whereas the introduction of extrinsic osmotic materials br 



whenever their capacities come to equilibrate those of the elastic 



filtration. Such obstacles do 



© 



it to 



standstill 



Tl 



effect of loss of osmotic property in the cell-sap may be retarded by 



recoil of the cell- 



obstacl 



to 





f 



