116 



Hydration and Growth. 



tein, and salt mixture lies below 46 C. and is probably above 40 C., 

 as both rate and total capacity become uncertain at 46 C. and above. 



The agar-oat protein mixture has a higher initial capacity at 46 

 to 47 C., but does not appear to absorb as much water as it did at 



TABLE 95. 



a temperature a few degrees lower. The probable error at the high- 

 est temperatures is great, however, and conclusions as to a separation 

 of initial rate and final capacity should be made with caution. 1 



The relation of temperature to swelling of agar and of these colloidal 

 mixtures is of interest because of the fact that they lie within the range 

 of activities of plants. The greater number of seed-forming plants 



6p.m. 



12 p.m. 



8a.m. 



FIG. 21. Tracing of auxographic records showing swelling of plates of agar 0.18 mm. in thickness 

 at various temperatures. The 5 mm. and 4-hour intervals of the record-slip are shown. 

 Increase is denoted by the downward movement of the pen, which amplifies the actual 

 increase 20 times. The initial and following rates are well illustrated. 



do not endure air-temperatures of above 45 or 46 C. The tempera- 

 ture of the stems or growing-zones in such exposures can not be cal- 

 culated from such data unless sunlight exposure is known. Actual 

 temperatures of the tissues have been taken by a few observers, from 



1 See Freundlich, H. Kapillarchemie, 1909, pp. 504-511, and references given also Ostwald, 

 W., Transl. by M. H. Fischer. An introduction to theoretical and applied colloid chemistry, 

 pp. 84-92. 1909. 



