^ 1 Trelease: Elongation of Banana Leaves 87 



sented such a large proportion of the total leaf elongation that 

 it alone might have been used as a close approximation of that 

 total, nevertheless it was considered advisable in the present 

 tests to employ the total elongation of all visible leaves. 



It must be mentioned here that the method just described 

 fails to take into account the growth of the young leaves 

 before they make their appearance above the false trunk, com- 

 posed of overlapping leaf bases. This method is, however, the 

 one which may be most satisfactorily applied to the growth of 

 banana and abaca plants. 



The results of these measurements are given in Table 1, which 

 shows the day and following night increments of total leaf elon- 

 gation of the ten banana plants, for the five consecutive days, 

 May 14 to May 18, inclusive. The table also shows the total 

 twenty-four-hour increment, and the ratio obtained by dividing 

 the night increment by the preceding day increment. 



In spite of the great variability of the different plants during 

 the same day and of the same plant during the different days, 

 the data shown in Table 1 illustrate the outstanding fact that, 

 as is true of most plant organs which have been studied in this 

 respect, these banana leaves usually elongated much more dur- 

 ing the night than during the day, this fact being brought out 

 by the records of individual plants as well as by the averages 

 for each day. As shown in Table 1, the average ratios of 

 night elongation to preceding day elongation for these five days 

 were 1.7, 5.5, 1.5, 2.5, and 3.3. The highest ratio value for 

 the whole series was 32.0, for plant 4 on May 15 to 16 (the 

 ratio for plant 3 on May 18 to 19 has no meaning, since there 

 was no measurable elongation during the day), and the lowest 

 ratio value was 0.2. For the first day, eight of the ten plants 

 showed greater elongation during the night than during the 

 day, one showed less, and one the same as during the day. For 

 the second day, nine plants showed greater elongation during 

 the night, and one showed less. For the third day, however, 

 only six plants showed greater elongation at night, and four 

 showed less than during the day. For the fourth day, eight 

 plants showed greater elongation during the night and two 

 showed less than during the day. For the fifth day, seven 

 plants showed greater elongation during the night, two showed 

 less, and one the same as during the day. 



Turning to the day and night rates themselves and to the 

 total twenty-four-hour rates, attention should be called to plant 



