It is a matter of doubtful argument how many species go to compose the genus Elm—Ulmus—owing to the uncertainty of distinguishing true permanent species from varieties and natural hybrids. Foremost botanists have differed widely on the question; for whereas Bentham and Hooker recognised in 1887 only two true species growing naturally in the United Kingdom, Elwes and Henry describe five native species, besides nine varieties of the wych elm, as many of the English elm, and no fewer than thirteen varieties of Ulmus nitens, a species hitherto classed as a form of the English elm.

The distribution of the elm family is somewhat peculiar, extending all the way from Japan, through Northern China and Europe to North America, but not crossing to the Western States; nor is any species to be found south of the temperate zone, except in the mountain ranges of Southern Mexico. Of all the cities of the New World, Boston reminds the British traveller more vividly of home scenes than any other, by reason of the massive English elms which enrich the landscape. Pity it is that we cannot return the compliment by planting the beautiful white elm (Ulmus Americana), the glory of Washington city, for it does not take kindly to our island climate.

The elm with which we are most familiar in the North is the wych elm (U. montana), easily to be distinguished from the English elm by the fact that it throws up no suckers from the root, whereas the English elm hardly ever ripens seed, and propagates itself entirely by suckers which it sends out as colonists to an astonishing distance—50 yards and more. There are exceedingly few authentic records of the English elm ripening seed in Great Britain; on the other hand, the wych elm sometimes produces a prodigious crop. In the spring of 1909 this tree presented a curious appearance. The foregoing summer had been a very warm one, stimulating the wych elm to such extraordinary efforts at reproduction that, before the leaves appeared, the trees seemed to be covered with fresh young foliage, which was really the crowded leaf-like seed vessels. In June these leaf-like membranes had become dry scales, each acting as parachute to a single seed, so that, under a hot sun and a high wind, the air was full of them—so full that they actually choked the eave-gutters of my house. Each of these little monoplanes carried the potentiality of a majestic forest tree; given a suitable resting-place, any one of these minute seeds might develop into an elm like those at Darnaway, in Morayshire, which in 1882 were 95 feet high, with clean boles up to 24 feet. So great was the exhaustion following upon the abnormal seed crop of 1909 that some of my elms were crippled by it, and two or three died outright.[9]

To produce well-shaped wych elms, timely pruning is essential, followed by close forest treatment, for no other tree spreads more wildly and wantonly, and unless means are taken to keep a single leader on each, the result will be very different from those lordly examples which stood, not many years ago, on the banks of the White Cart at Pollok, four of which were figured by Strutt in his Sylva Britannica in 1824. The largest of these measured in that year 85 feet in height and 11 feet 10 inches in girth, and contained 669 cubic feet of timber. Two of this group were blown down in the great gale of 22nd December, 1894, and the remaining pair were felled in 1905, being respectively 90 and 96 feet high. The age of these giants was shown by the annual rings to be about 300 years.

The weeping elms which one sometimes sees in gardens is a variety which originated in a Perthshire nursery about one hundred years ago. It is very ornamental, though it never attains much height, being perfectly flat-topped. As it can only be propagated by grafts, a sharp lookout must be kept to prevent the stock outgrowing the scion.

The wych elm is indigenous over the whole of the northern part of Great Britain, the largest recorded being at Studley Royal, in Yorkshire—105 feet high and 23 feet in girth at 5 feet up in 1905. As an element of the primÆval Scottish forest, the wych elm must have been held in high esteem, judging from the number of Gaelic place-names commemorating it. The old Gaelic name for it was leam, plural leaman (pronounced "lam" and "lamman"). Ptolemy's Leamanonius lacus is now Loch Lomond, the lake of elms, out of which flows the Leven, which is the more modern aspirated form leamhan (pronounced "lavan"); and we find the same association of names in eastern Scotland, where the Lomond Hills overlook the town of Leven. The Lennox district was formerly written Levenax, which is the adjectival form leamhnach (lavnah), an elm wood. The rivers Lune and Leven in Lancashire (Ptolemy's Alauna), the Leven in Cumberland, and the Laune at Killarney all seem to indicate the former existence of elm woods on their banks. In the name Carlaverock is probably preserved another derivative—caer leamhraich, the fort among the elms.

It was long supposed that the English elm (U. campestris) was not indigenous to England, seeing that it never propagates itself in these islands by seed. Its presence was explained by the convenient device of attributing its introduction to the Romans; but there is not a shred of evidence in support of this conjecture. The elm of Italy is quite a distinct species, according to Elwes and Henry, a fact with which Shakespeare, though familiar with "Warwickshire weeds" (as elms are called near Stratford-on-Avon), may not have been acquainted when he made Adriana plead with him she believed to be her husband:

Come, I will fasten on this sleeve of thine;
Thou art an elm, my husband, I a vine;
Whose weakness, married to thy stronger state,
Makes me with thy strength to communicate.

The English elm, however, grows luxuriantly in Spain, and ripens seed abundantly there, the tradition being current that it was introduced from England to the Royal Park at Aranjuez when Philip II. was laying out that demesne. Dr. Henry, however, considers it not improbable that this tree is truly indigenous in Spain, and that it is certainly so in the southern counties of England, where, as aforesaid, it reproduces itself only by suckers. Other examples are not wanting of certain plants yielding to climatic conditions, by resorting to reproduction by suckers and ceasing to produce seed.

Perhaps the most striking display of the true English elm to be found anywhere is the magnificent quadruple avenue known as the Long Walk, at Windsor. Many of these are 120 feet high and 15 feet in girth. The avenue leads from the Castle gates to the statue in the park, a distance of two miles and three-quarters. Taller individual elms may be seen elsewhere, as in the grounds of King's College, Cambridge (130 feet), Boreham House, in Essex (132 feet), and Northampton Court, Gloucestershire (150 feet by 20 feet in girth). The last-named tree, by the way, may no longer be seen, for it was blown down in 1895, but there can be no doubt about its dimensions, which were accurately ascertained as it lay on the ground. It was probably the champion of that particular species in England; but it was inferior in bulk to the great elm which stood in the grounds of Magdalen College, Oxford, until it was blown down in April, 1911, pronounced by Mr. Elwes to be "the largest elm I have ever seen and the largest tree of any kind in Great Britain."[10] Mr. Elwes carefully measured the fallen giant, finding it to be 142 feet high, 27 feet in girth, and containing 2787 cubic feet of timber. He and Dr. Henry pronounce it to have belonged to the variety or sub-species classed as the smooth-leaved Huntingdon or Chichester elm (U. vegeta, Lindley), although in this case no suckers had been produced, which the Huntingdon elm usually sends up in profusion.

It is usually stated in forestry manuals that the English elm is not suited for Scottish conditions. My own experience is directly opposed to that view, for, having some score or so of these trees now about 110 years old to compare with wych elms planted at the same time, the English species exceeds the other in height and equals it in bulk. Two English elms at Loudon Castle, in Ayrshire, were measured in 1908, and were found respectively to be 107 feet by 15 feet 4 inches and 105 feet by 16 feet 4 inches.

I have found, however, that by far the shapeliest and best elm for Scottish planting is the smooth-leaved elm, formerly, and probably correctly, considered to be merely a permanent variety of the English elm (U. campestris), but now distinguished as a species under the title of Ulmus nitens. It certainly resists violent winds better than the English elm, being therefore preferable for sea exposure. Moreover, its timber is esteemed more highly than that of other elms, being remarkably tough. Dr. Henry has distinguished a variety of this elm as Italica—the Mediterranean elm—which is the kind used by Tuscan vine-dressers to train their vines on.

The smooth-leaved elm is of less sprawling habit than the wych elm, but occasionally it takes advantage of space to spread out of all measure. Of this there is an example at Sharpham, near Totnes, where a tree of this species has covered the space of a quarter of an acre, some of its side branches being 104 feet long. The total height was between 80 and 90 feet in 1906, in which year it was figured in the Gardeners' Chronicle as a wych elm. Mr. Elwes, however, pronounces it to be of the smooth-leaved kind. On the other hand, the Cornish elm, which is a variety of U. nitens, is usually of columnar habit.