STUDIES ON ULMUS : I 



139 



the ratio : length between the transverse axes marking the lowest point on each side of 

 the leaf /lamina length. The tendency towards obverse configuration, which may con- 

 veniently be termed obversity, is calculated from the ratio : length between the transverse 

 axes marking (1) the point of maximum breadth on the shorter side of the leaf and (2) the 

 point where the longer side runs into the petiole/lamina length. 



In addition, it is noted whether the upper surface of the leaf is scabrpus or smooth. 

 Although gradations exist in this characteristic, a convenient method of measuring 

 scabrosity was not found. Scabrous leaves will be denoted hereafter by an asterisk *, 

 smooth leaves by a dagger t. 



Fig. 1. Area of survey. The solid line represents major square 52 of the Ordnance Survey. The broken 



line represents the eastern boundary of U. procera. 



From these primary measurements, means for each character per tree are calculated, 

 together with their standard deviations. Then, for each pair of fairly similar trees, the 

 t test for significance of difference between means (P = 0-05) is made for each character. 

 A record is made of all pairs of sample trees which do not differ significantly in any of 

 the five characters studied. 



Results 



Specimen samples from each minor square in which elms were encountered are 

 illustrated in Fig. 2. Where two samples were obtained from one minor square, they 



