96 The Philippine Journal of Science 



the leaves had apparently recovered the degree of saturation 

 ^tZy had Z at 8 a. m. Other observations of banana 

 plants showed that, although maximum expansion of the leaf 

 wings usually occurred shortly after sunset, the plant as a whole 

 toe more turgid later in the night, this being indicated by 

 ^creasing rigidity and elevation of the leaf midribs, as well 

 a S by a slightly greater diameter of the false trunk composed 

 of overlapping leaf bases. The maximum expansion of the leaf 

 wings was maintained throughout the night, and the wings 

 began to approach each other again soon after sunrise on the 

 succeeding day. «*».* 



It appears that the turgor movements of such leaves as those 

 of the banana furnish an index of leaf turgidity, and hence of 

 leaf water content. If this be true, then the apparent leaf width 

 might be an index of the rate of leaf elongation; and it might 

 be possible, by employing this index, to relate the difference 

 between the nocturnal and diurnal elongation rates, discussed in 

 the first part of this paper, to corresponding differences in turgor. 

 As is well known, enlargement does not take place in plant cells 

 that are not turgid; enlargement requires an excess in the rate 

 of water intake, above that of water loss. It is suggested that 

 the two groups of phenomena dealt with in this paper may be 

 closely related through the same causal condition, turgidity. 

 But the experimental observations for growth rates and for leaf 

 movements were not made for the same periods, and hence no 

 direct evidence is available in this respect. 



