Imbibition and Growth in Fruits. 



163 



below, then dried, and swelled again, with results as shown in table 119 

 at 16°C.: 



Table 119. 



The unsatisfied water capacity of these sections taken from young 

 terminal internodes was comparatively great, doubtless due in part to 

 the constant drain of the active leaves they bore. The older wood, in- 

 cluding that formed the previous year, showed an absorptive capacity 

 of 22 per cent in water. It is from these older internodes that the nuts 

 arise. 



The nuts were highly turgid, exuded sap when cut into, and hence 

 must have had a colloidal composition which acted to withdraw water 

 from the stems, which were less highly hydrated. The soil was low in 

 moisture-content at this time, as. it had been 4 or 5 months without 

 rain. 



Tests of nuts 8to 10mm., from which tangential sHces had been removed 

 to give a uniform thickness of 7.5 mm., were made in July, and these 

 swelled at temperatures of 17° to 20° C, in solutions as follows: 



Table 120. 



p. ct. 



Distilled water 1.4 



Citric acid, 0.01 M 1.8 



Potassium hydroxid, O.OIM 1.4 



Potassium nitrate, 0.01 M 2 



A useful conception of the hydration conditions in the stems and 

 bruits may be formed, if due weight is given to the measurements cited 

 above. The woody branches of the previous year, on which both the 

 leafy green twigs and those bearing the nuts are borne, had a relatively 

 large deficiency in water, so that sections a few centimeters long absorbed 

 about 20 to 25 per cent of their volume of distilled water in 24 hours at 

 20° C. No swelling test was made, but it is obvious that an enlarge- 

 ment of only a small fraction might be shown by this or any branch 

 with a mature woody cylinder. The active green twigs still in a state 

 of elongation arising from these branches had a swelling capacity of 10 

 per cent. The growing nuts arising from the drier stems exuded water 

 from cut surfaces, the cotyledons being sacs of watery fluid, in contrast 

 to the dry appearance of sections of the youngest internodes, and showed 

 a swelling of less than 2 per cent and soon shrunk when placed in a cylin- 



