There is no group of trees whereof the scientific nomenclature has become so hopelessly confused as the _Pomaceæ_, a sub-order of the vast rose order. The group itself divides itself naturally into seven sub-groups or sections, which some botanists treat as independent species; but British foresters need to concern themselves with only five of these sections--namely (1) _Sorbus_, the rowan; (2) _Aria_, the whitebeam; (3) _Hahnia_, the wild service tree; (4) _Pyrophorum_, the pears; and (5) _Malus_, the apples. Some people may feel impatient with these niceties of classification, and declare that popular names serve all useful purpose; but many of these trees are very beautiful, well deserving the attention of planters, who are sure to be disappointed in being served with the wrong species unless they are at the pains to know exactly what they order from nurserymen, and are able to identify the plants when they get them. The rowan tree (_Pyrus aucuparia_) is of humble stature, seldom exceeding 40 feet; nevertheless, we should be losers if it disappeared from our woodlands, not only because of its beauty and the delicious diet which it affords to birds, but because of the peculiar veneration with which, in primitive times, it became invested in Northern Europe. The Norsemen held it to be a holy tree, consecrated to Thor, and their faith in its protective virtues became deeply implanted in the folk-lore of our own country. Rowan-tree and red thread Gar the witches come ill-speed. It has been suggested that the singular expression, "Aroint, thee, witch!" occurring nowhere in English literature except in _Macbeth_, Act 1, sc. 3, is a corruption of "A rountree, witch!" but the late Professor Skeat sternly refused to entertain that explanation. Anyhow, so long as belief in witchcraft endured in this country, a branch of rowan was esteemed a sure protection against evil spells. In many a Scottish byre a bunch of rowan may still be seen suspended, and a common feature in cottage garden plots consists of a couple of rowan saplings planted before the door, with their tops plaited together to form an arch, so that comers and goers shall thereby derive protection against witchcraft by passing under the tutelary boughs. [Illustration: FLOWERS OF THE ROWAN (_Pyrus aucuparia_)] In Strathspey it used to be the custom to cause all sheep and lambs to pass through a hoop of rowan wood on the 1st of May, and flocks and herds were driven to the summer shieling with a rod of the same wood. In some parts of England the rowan is still called the "witchen." Evelyn wrote of it under that name, and said that in his day (1620-1706) the tree was reputed so sacred in Wales "as that there is not a churchyard without one of them planted in it; so on a certain day in the year everybody religiously wears a cross made of the wood."