© 1959 by Institute of Chartered Foresters
STUDIES ON ULMUS
III. The Village Elms of Hertfordshire
Commonwealth Bureau of Plant Breeding and Genetics Cambridge
A biometrical study of the elms of southern Cambridgeshire was published in Forestry, xxxi. 132. The present paper is a parallel study of the village elms of Hertfordshire. The number of samples collected was 143. For each of these, 8 quantitative and 1 qualitative foliar character were determined. The majority of the samples fall into 9 biometrically defined groups, 7 pertaining to U. carpinifolia and 2 to U. procera. U. glabra was also encountered and one putative hybrid between U. glabra and U. carpinifolia.
The U. carpinifolia elms occur in the east of the county and appear to be of Roman introduction in at least one case. Of the two groups of U. procera, one with short petioles and low basal asymmetry is centred around St. Albans. The other group, with longer petioles and conspicuous basal asymmetry, appears to have entered the county both from the Icknield zone in the north and from Middlesex in the south. Both groups of U. procera were established by the end of the Middle Ages, but their introduction into the county has not yet been closely dated.