86 The Philippine Journal of Science 1923 



The study was made in 1919, during the latter part of the dry 

 season (May), at the College of Agriculture, Los Banos, Laguna, 

 Philippine Islands. It is a pleasure to acknowledge indebtedness 

 to Prof. B. E. Livingston for suggestions in the preparation of 

 this paper, and to Mr. Felix Maceda for assistance in securing 

 the measurements. 



LEAF ELONGATION 



The leaf elongation of ten selected plants was measured at 

 6 a. m. and at 6 p. m., for five days. The method used was 

 based on that described by Copeland 4 for measuring leaf enlarge- 

 ment of the youngest visible leaf of the coconut. A transverse 

 line was drawn with ink across the bases of the youngest leaf 

 (leaf 1) and the next to the youngest leaf (leaf 2) where the 

 latter overlapped the former, about half of the line being on 

 each leaf. Since the two adjacent leaves do not elongate at the 

 same rate, the two parts of this line are soon shifted with 

 reference to each other, one leaf sliding upon the other as growth 

 proceeds. At the end of the twelve-hour period the vertical 

 distance between the two parts of this line showed the difference 

 in elongation between the two leaves. A similar line drawn 

 across the bases of leaf 2 and the next older leaf (leaf 3) was 

 used to measure the difference in elongation between these two 

 leaves. Older leaves were marked and observed similarly, it 

 being assured that the oldest leaf considered had already ceased 

 to elongate at the time of marking. The sum of all the differ- 

 ences thus shown was taken as a measure of the elongation of 

 the youngest leaf, for the period. 



It is evident that if a represents the distance between the 

 two line parts for leaves 1 and 2, b the corresponding distance 

 for leaves 2 and 3, c the distance for leaves 3 and 4, d the dis- 

 tance for leaves 4 and 5, etc., then the entire elongation of leaf 



1 is measured by the sum a + b + c + d + + I, in 



which I represents the measured distance for the oldest pair of 

 eayes showing any measurable shifting of the line parts. Simi- 

 larly, the growth of leaf 2 is given by b + c + d 4- 



+ Z;of leaf3 by c + d + + *; of leaf 4/by tf -^ '. ". *. *. \ 



+ 1; and, finally of leaf n, by I, there being n elongating leaves. 

 The elongation of all visible leaves taken together is represented 

 by the sum of the series a 4- 2b + 3c + U + + n l 



Although the enlargement of the youngest visible leaf repre- 

 • Copeland, E. B., The Coco-nut. London, Macmillan and Co. (1914) 212. 



