GABRIELLE L. C. HOWARD. 85 



for measurement and in many types the change between these 

 and the significant leaves is very gradual. It is probable that in 

 America the general uniformity of the kinds grown makes this 

 method more applicable. 



The actual procedure adopted in these investigations was 

 as follows. Very small cardboard labels were prepared with 

 the number of the plant and culture, and these were threaded 

 with fine copper wire. These labels could be readily affixed to 

 the leaf by passing the ends of the copper wire through the mid- 

 rib, and bending them flat on the under side. The individual 

 leaf chosen by the investigator for measurement was immedi- 

 ately labelled in this manner while on the plant. The leaves 

 could then be removed and measured in some convenient place. 

 The leaf after measurement was pressed with the label still 

 attached, and thus a complete record of all the plants examined 

 has been preserved. It is hoped to use this material in dis- 

 entangling the factors which are concerned in the shape of the 

 leaf. This method of attaching a label, which lies flat on the 

 mid-rib, and therefore interferes with no measurement of the 

 leaf while still on the plant, has proved most useful. The 

 labour of preparing these labels, threading the wire, and the 

 subsequent drying of the leaves, however, would not be possible 

 for several thousand plants except for the cheap labour avail- 

 able in India. A second and a third leaf can be removed 

 immediately above or below the first one chosen. 



The venation of the leaves was determined by measuring the 

 angle between the mid-rib and the lateral vein with a horn 

 protractor. Only differences of 5° were noted. Experience 

 showed that such determinations gave good results, and that 

 the error generally was not more than 15°. These measure- 

 ments were carried out in two ways, either while the leaf was 

 still attached to the plant or on the detached leaf which had been 

 selected for other measurements. The first method has the 

 advantage that all the leaves can be examined in a general 

 manner by eye at the same time as the measurements are made ; 



