The foliage of the Birch in autumn turns to a yellow hue. At this period--and, indeed, for a month earlier--there may be seen beneath the Birch-trees one of the most striking of our toadstools, the Fly Agaric (_Amanita muscarius_), so-called from its use as the lethal ingredient in the making of fly-papers. From a bulbous base a creamy yellow stem arises, decked about half its height with an ample hanging frill. The upper side of the spreading "cap" is painted with crimson, over which are scattered flecks of white or cream kid--the remains of an outer envelope that was ruptured by the expansion of the cap, and of which the frill represents the lower portion. This species is really poisonous, and the Kamschatkans are said to make their _vodka_ superlatively intoxicating by the addition of this fungus to it. On the trunk of the Birch may sometimes be found a large fungus named _Polyporus betulinus_, whose root-like portion penetrates the bark and sucks up the sap. Birch-bark is used for tanning certain kinds of leather, and the peculiar odour of Russian leather is said to be due to the use of Birch in its preparation. The Birch agrees with the Beech in two respects--it is of little value for timber, but as a nurse to young timber-trees it is of considerable importance. Its name is from the Anglo-Saxon _beorc_, _birce_, and signifies the Bark-tree. * * * * * [Illustration: _Pl. 17._ Alder--summer.] The Alder (_Alnus glutinosa_). Although the Alder is abundant by riversides and in all low-lying moist lands as far north as Caithness, it is not so generally well known at sight as the Oak, the Beech, and the Birch. It is a small tree ordinarily only thirty to forty feet in height, with a girth from three to six feet, though occasionally it aspires to seventy feet in height. This is when it is growing in moist loam, upon which rain or floods have washed down good layers of humus from woods at a higher elevation. If, with its roots thus well cared for, its head is in a humid atmosphere, the Alder is in happy case. If it has had the misfortune to get into a porous soil, though this may be moist enough to please an Ash, the Alder becomes merely a big bush. [Illustration: Alder.]