Imbibition and Growth in Fruits. 



169 



If this method be followed it would at once be obvious that while the 

 rate of increase in diameter would be a direct measurement, yet as the 

 fruit increases as a globe the actual material added could be regarded 

 as a shell on this globe. The rate in terms of volume would therefore 

 be the amount of this shell to be calculated by finding the difference 

 between the initial volume and the volume at the end of each period. 

 The rate by direct measurement of diameter and by volume increases 

 may be compared as in table 121, for periods of one week beginning 

 on the date given. 



Table 121. — Average daily rate of growth. Table 122. 



The rate on September 11 by direct measurement would appear to 

 be one-tenth that of a month earlier, yet actually water and new mate- 

 rial was being added at a rate equivalent to one-fourth of the earlier 

 rate. The radial proportions would make the rate on August 21 not 

 much more than 40 per cent of the rate on August 9, while the increase 

 in volume was over 96 per cent. The rate in the week beginning 

 August 28 would appear to be less than a fourth that by direct measure- 

 ment on August 9, yet actually the increment of water and material is 

 more than half that in the younger stage and smaller size. 



A second plant with the auxograph arranged to take axial varia- 

 tions in the fruits which measured 33 mm. was arranged to run con- 

 currently with No. 1 and under identical temperature and conditions 

 of moisture. The daily rates of increase in diameter were as shown 

 in table 122 for weeks beginning on the dates given. 



Here again the actual course of growth as calculated in terms of 

 volume shows that simple measurements of the thickness do not express 

 the real values in growth of such organs. 



The third test was made on a fruit taken at a much earlier stage at a 

 diameter of 16 mm. with a transverse or radial bearing, the tempera- 

 ture and moisture conditions being similar to those of 1 and 2. The 

 daily rate of increase was as shovm in table 123 for the weeks begin- 

 ning on the given dates. 



The actual volume of this fruit at the close of the experiment was 

 approximately 2,900 c. mm. and its growth had been followed for a 

 period of 40 days. It is notable that in the earlier stage in the advance 

 of the fruit from 20 to 26 mm. in diameter (August 21 to August 31), 

 while the increase of the diameter seems constant, yet the actual 



