WORK DONE AND CONSUMPTION OF ENERGY 31 



At a velocity of a mm. per minute, 0-22 erg of work would be done 

 per minute per gram of moving plasma, instead of the 0-18 erg per gram 

 per minute as calculated in the case of the same liquid flowing through 

 a capillary tube of o-i cm. diameter. This slight discrepancy is not 

 surprising considering the dissimilar modes of calculation. 



On a somewhat similar basis O. MUller l has calculated that the work 

 done by the protoplasmic band of a diatom against the friction of the 

 surrounding water varies from 56,285 to 830,413 8 p. units of work per 



second (5 = ^^ ^^ ^^ milligram). This equals from 0-000,000,005,6 to 



0-000,000,008 erg. But it would take about 400,000 of the diatom 

 Nitzschia sigmoidea to make one cubic centimetre. 



Hence if we take the density of the diatom as being 2 (Muller, 1. c.), 

 and if the streaming plasma forms \ of the bulk, then the work done per 

 gram of moving plasma would be 0-564 to 0-864 er g P er minute, values 

 higher than those given above. The diatom in question moves with an 

 average rapidity of i mm. per minute (cf. Vallisneria), and Muller has 

 calculated that the velocity of streaming in the external bands must be 

 about 3 mm. per min. (cf. Nitella). 



SECTION u. The relation between the work done in streaming and 

 the consumption of energy. 



The amount of energy that can be expended upon a partial function 

 such as streaming must always be strictly limited, and the ratio between 

 the total energy of respiration and the amount expended in streaming 

 varies in different plants, and in the same plant at different temperatures 

 and under different conditions. Nevertheless, the minimal amount of 

 oxygen-respiration at which streaming can remain active in an aerobic 

 plant will afford some indication as to the maximal amount of energy 

 that could possibly be expended in this way. Stich found that oxygen- 

 respiration continues, though weaker than usual, at a partial pressure of 

 oxygen corresponding to 20-30 mm. of mercury (3-4 per cent, oxygen), 

 while Clarke has shown that streaming commences at a partial pressure 

 of from i to 4 mm. of mercury, and becomes fairly active before the 

 pressure reaches 10 to 15 mm. 2 



A few determinations of the respiratory activity of Chara were made 

 in the following manner. Plants were placed in a darkened vessel con- 



Ber. d. D. Bot. Ges., 1896, Bd. xiv, p. 117. 



Stich, Flora, 1891, p. 13; Clarke, Ber. d. D. Bot. Ges., 1888, p. 273. 



