226 



HEAT AND PROTOPLASM 



[CH.YIII 



measurements were made, also, by SCHULTZE, on Tradescantia 

 hairs. But the work of neither of these equals in importance 

 the determinations of VELTEN ('70), which I propose to give 

 in some detail. He determined the time consumed by the 



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FIG. 68. Curves showing the relation between temperature (abscissae) and rate of 

 movement per minute of the chlorophyll grains floating in the protoplasm of the 

 cells of three species of greeu plants. (Data from VELTEN, '76.) 



floating chlorophyll grains in cells of Elodea canadensis and 

 Vallisneria spiralis, or the small granules near the wall of cells 

 of Chara in traversing 0.1 mm., at various temperatures. The 

 results in modified form are given graphically for these three 

 species in Fig. G8. In this figure, the ordinates represent 

 distance (in millimetres) traversed in 1 minute. The abscissae 



