There are about five-and-twenty known species of alder, all bearing a considerable family likeness, and none exceeding in stature our only native species, _Alnus glutinosa_. Of this, many specimens might be mentioned between 70 and 90 feet high, though it is often difficult or impossible to obtain right measurement owing to the trees growing beside rivers or lakes. The most remarkable alder wood known to me is at Kilmacurragh, in County Wicklow. In the old spacious days the ground it occupies was a deer park. The trees are ancient, but not very lofty, from 50 to 60 feet high; but many of them have clean boles up to 30 or 40 feet and girth from 8 to 10 feet. One of them had a girth of 11 feet 4 inches in 1906. In the swampier parts of the wood, some of the trees have got bowed; their trunks present a curious appearance from being densely covered with pennyroyal (_Cotyledon umbilicus_). There can be little doubt that this grove is a fragment of the primæval Irish forest.
There are some very fine alders beside the Gade in Cassiobury Park, Herts, one of which Dr. Henry made out to be 85 feet high, with a girth of 11 feet 6 inches; but these dimensions were exceeded by an alder 90 feet high with a girth of 11 feet 4 inches at Betchworth Park, Surrey, and by one at Enville Park, Stourbridge, 87 feet high, with a girth of 8 feet 2 inches.
In Scotland the tallest measured by him was at Scone--66 feet high by 6 feet 3 inches in girth; but no doubt there are bigger alders than that north of the Tweed, though it might not be possible to match a shapely tree measured in 1904 at Churchill, Co. Armagh, which stood 94 feet high, girthing 6 feet 4 inches, and having a clean bole of 60 feet.
The aforesaid tree at Scone is of the cut-leaved variety, a sport which, originating in France, and being planted in De la Berlière's garden near Saint-Germain, says Loudon, became the parent of all that are now to be found. It is certainly more ornamental than the common form, the leaves being divided half-way to the midrib into three to six segments on each side.
The alder is not rated high among us as a timber tree, though good boles are sometimes in request, for what precise purpose I cannot tell. Mr. Elwes states that he sold three hundred alders standing for £100, which he reckoned to be at the rate of 4d. or 5d. a cubic foot. This must be considered an excellent return from land that was fit for no other crop. Clogmakers take alder of suitable size as readily as birch, giving as much as £40 an acre for coppice, which will be fit for cutting again in twenty years. One of the most picturesque scenes in forestry is a summer encampment of clog-cutters.