The elms of Wales

Two methods of biometrical analysis were used to characterizea collection of 178 leaf samples assembled in the course ofan all-Wales survey of elms made in 1977–78. All sampleswere referable to either U. glabra, U. minor var. minor, U.minor var. vulgaris (= U. procera)orU. x hollandica. The variationwithin each taxon is described. Elm regions are demarcated tosupplement those already described for England. U. glabra isthe only elm believed to-be native. It is thought most likelythat the main Welsh population of U. minor var. vulgaris, inGlamorgan, was introduced from Somerset some time before theNorman Conquest. U. minor var. minor is rare throughout Walesand could be of 18th century origin; its possible spread alongdrovers' routes is considered. Some notomorphs of U. x hollandicamust have been introduced as such. Others probably arose inWales from hybridization involving U. glabra, U. minor var.vulgaris and U.x hollandica var. hollandica.     

Studies on Ulmus: VI. Fenland Elms

A biometrical study of the leaves of the elms of the Isle ofEly and of the Parts of Holland, Lincolnshire, is presented.The number of samples totalled seventy. Elms are sparsely distributedin the Fenland except in the Island of Ely. Most of the samplespertain to one of four groups of U. carpinifolia, to U. procera,to U. glabra or to the Dutch Elm. No type of elm is believedto be indigenous in the area. The only elms likely to be ofancient standing are two of the groups of U. carpinifolia inthe Island of Ely, one of which was probably introduced fromthe Cam valley and the other from Huntingdonshire about theRoman era. The mosaic of elm types in the northern Fens arebelieved to be much more recent, in many cases post-medieval;some of these, as at Thorney, were probably introduced as seedfrom the continent.     

Isoperoxidase Variation in Ulmus L

Isoperoxidase zymograms are presented for leaf extracts of 69English and 16 exotic elm trees. The commonest zymogram wasfound in some samples of six species in four sections of thegenus, and is presumed to be ancestral. Wide variation was foundin the sexually reproducing species U. glabra in contrast tothe relatively invariant zymograms of the mainly vegetativelyreproducing U. minor.     

Studies on Ulmus: VII. Essex Elms

This biometrical study is based on a collection of nearly 500leaf samples from every ancient parish in the county. Most ofthe elms could be assigned to one of nineteen groups, 9 of U.carpinifolia, 1 of U. glabra, 2 of U. procera, 3 of putativeF₁ U. carpinifolia x U. glabra, 3 of U. carpinifolia with suspectedintrogression from U. glabra, and 1 of U. carpinifolia x U.procera. U. glabra is indigenous. Most of the U. carpinifolia appearto have spread out from six centres of origin, mostly near thecoast. These elms are very similar to forms now occurring innorth-west France, and it is thought probable that they wereintroduced from there, possibly by the settlers responsiblefor the Red Hills salt workings shortly before the Roman occupation.One group of U. carpinifolia came from Cambridgeshire via theEssex branch of the river Cam. Of the two main populations ofU. procera, that characteristic of south-east Essex is believedto have come from northern Kent, probably from the Hoo peninsula,while the group found in south-west Essex is probably a laterintroduction from further west. Hybridization between introduced U. carpinifolia and nativeU. glabra has occurred on a very large scale and putative F₁hybrids extend in a broad band across the county from the Hertfordshireborder to Suffolk. This hybridization most likely occurred duringthe clearing of the heavily forested part of northern Essexin pre-Conquest times. Subsequently, back crossing occurredbetween these hybrids and U. carpinifolia. Occasional hybridizationalso seems to have occurred between U. procera and the othertwo species. An outline of the probable history of the elm in eastern Englandas a whole concludes the paper.     

STUDIES ON ULMUS: III. The Village Elms of Hertfordshire

A biometrical study of the elms of southern Cambridgeshire waspublished in Forestry, xxxi. 132. The present paper is a parallelstudy of the village elms of Hertfordshire. The number of samplescollected was 143. For each of these, 8 quantitative and 1 qualitativefoliar character were determined. The majority of the samplesfall into 9 biometrically defined groups, 7 pertaining to U.carpinifolia and 2 to U. procera. U. glabra was also encounteredand one putative hybrid between U. glabra and U. carpinifolia. The U. carpinifolia elms occur in the east of the county andappear to be of Roman introduction in at least one case. Ofthe two groups of U. procera, one with short petioles and lowbasal asymmetry is centred around St. Albans. The other group,with longer petioles and conspicuous basal asymmetry, appearsto have entered the county both from the Icknield zone in thenorth and from Middlesex in the south. Both groups of U. procerawere established by the end of the Middle Ages, but their introductioninto the county has not yet been closely dated.