1839.] 



their Relation to Oxygen Pressure. 



371 



for the various tissues of different plants would not vary any more 

 among themselves than do the actual results obtained for naked 

 plasmodia. 



The age of the cell or plasmodium and the conditions under which 

 it has been developed to some extent influence the minimum oxygen 

 pressure necessary to restore movement. 



The time taken by the protoplasm to recover its streaming move- 

 ment is too short to be measured in cases where the conditions are 

 favourable, as in young hairs and in slender threads of plasmodia, 

 but increases with cuticularisation of the cell wall, the age of the cell, 

 and the length of time between the cessation of movement and the 

 introduction of the necessary oxygen supply. 



Very slight irritation of the plasmodia during the experiment 

 causes them to contract towards definite centres where the protoplasm 

 assumes a more or less spherical condition. 



Temporary deprivation of oxygen in a cell showing circulation 

 induces a simplification in the arrangement of the protoplasmic 

 strands. In the leaf cells of Elodea for example the circulation may 

 occasionally pass over into rotation. 



After the streaming in plasmodia has been restored by the intro- 

 duction of the necessary oxygen pressure it ceases again in a very 

 short time. The movement in fact can be maintained only by 

 constant small additions to the oxygen pressure. This is not caused 

 by the consumption of the oxygen in the immediate neighbourhood. 



Amoeboid movements continue in an atmosphere of hydrogen for 

 some time after the streaming has ceased. 



After ciliary movement is arrested in any healthy infusorian by 

 the absence of oxygen the organism soon begins to disintegrate. 

 The introduction of an oxygen pressure of about 1 mm. is sufficient 

 to arrest disintegration and restore ciliary movement, provided the 

 breaking up has not proceeded too far. 



The growth of the plant and the streaming of protoplasm in the 

 active cells thereof appear to be parallel phenomena, streaming, or at 

 least the pow r er of very rapidly assuming the streaming movements, 

 being possessed by the parenchyma and probably the phloem of plants 

 so long as they continue to grow in an atmosphere of hydrogen. 

 Inability on the part of the protoplasm to continue its movements 

 seems to be always associated with total cessation of growth. 



