Turning now to the true black poplar (_Populus nigra_), we find that this species, a native of Midland England, but probably not of Scotland, has become established in the eastern United States, having been introduced there by British colonists. It has often been confused with the black Italian variety, but may easily be distinguished in this country by the large burrs on the trunk, by its earlier leafing, and by the young foliage being green, instead of reddish, as in the black Italian. The true black poplar also sheds its leaves much earlier in autumn than does the other. It is not a tree commonly planted in Scotland, but there are specimens ranging from 90 to 100 feet high at Dalzell, Ross, and Cambusnethan, in Lanarkshire; at Auchentorlie, on the Clyde; and at Smeaton-Hepburn, in East Lothian. The variety of this tree so well known as the Lombardy poplar forms a notable feature in the landscapes of Southern England, Central and Southern Europe, and a great part of Asia. As it can only be propagated by cuttings, it is believed that all the millions of Lombardy poplars spread over the continents of Europe and Asia originated with a single "sport" growing on the bank of the river Po early in the eighteenth century. Probably the first of its race was brought to England about 1750 by the third Duke of Argyll, and planted by him at Whitton, near Hounslow. This tree, which has now disappeared, was measured by Loudon before 1838 as 115 feet high. [Illustration: WHITE POPLAR (_Populus alba_) IN JULY] [Illustration: WHITE POPLAR (_Populus alba_) IN DECEMBER] One peculiarity of the Lombardy poplar I do not remember to have seen noticed by any writer on forestry. Other poplars of all sorts, including the black poplar whereof this is only a variety, mingle branches freely with their neighbours; but the Lombardy poplar is a regular _Sainte-Nitouche_, and will not suffer contact with any other tree, even one of its own race. A curious example of this may be seen in London. When the Buckingham Palace Hotel was built, somewhere about 1860, Queen Victoria desired that a screen of trees should be planted within the Palace enclosure to shut the hotel out of view. The Office of Works chose the Lombardy poplar, calculating that it would form a lofty, thick hedge. Not a bit of it! The trees died rather than touch each other; they have been replaced times without number; but the Office of Works has never discerned the secret of their temperament, and continue their task of Sisyphus year after year, filling the gaps caused by death with trees of the same kind. Had a row of true planes been set there at first, the privacy of the Palace would have been secured long before this.