Larch plantations sometimes present the appearance of death whilst they are still covered with foliage, but the leaves are yellow and twisted. This most frequently occurs in the case of trees between the ages of ten and fourteen years, and is due to the depredations of a leaf-mining caterpillar, which ultimately changes into a minute moth, the Larch-miner (_Coleophora laricella_). It feeds in the interior of the Larch-needles, and therefore is beyond the reach of destruction, except by felling and burning affected trees, to prevent the spread of the pest. Its ravages keep the tree in ill-health, and apparently prepare the way for the deadly attack of another small enemy, known as the Larch Canker--the fungus _Peziza willkommii_. Sickly trees are also liable to the attentions of a Wood-wasp (_Sirex juvencus_), whose appearance is usually the cause of a little terror in nervous persons. It has two pairs of smoky transparent wings, and its stout, straight, blue body terminates in a long slender point. Its large white grub spends two or three years tunnelling towards the heart of the tree and out to the bark again, but rarely attacks sound trees. It sometimes makes its appearance in a house from wood that has been used for building purposes. [Illustration: _Pl. 156._ Flowers and Cone of Larch.] The Silver Fir (_Abies pectinata_). Evelyn has left on record the fact that a two-year-old specimen of the Silver Fir was planted in Harefield Park, near Uxbridge, in the year 1603, and this is usually regarded as the date of its introduction to England, though the evidence is by no means conclusive. Its home is in the mountain regions of Central and Southern Europe. Its highest range appears to be on the Pyrenees, where it is found at an elevation of 6500 feet, forming pure forests of considerable area. Specimens have been recorded in Southern Germany that have attained a height of nearly 200 feet, but in this country a more usual stature is from 100 to 120 feet, with a bole girth between 10 and 15 feet. Its trunk is straight and erect, tapering gently, and covered with smooth bark, of a greyish-brown colour, which in aged specimens becomes rugged and fissured longitudinally, as shown in our photo, and of a silvery grey colour. It retains its lower branches for a period of forty to fifty years, but after that age they begin to fall off. Whilst the tree is growing up--which is, roughly speaking, during its first two hundred years--the crown forms a slender bush; but its vertical growth completed, the crown grows laterally, and becomes flat-topped. Its life-period covers about four hundred years. [Illustration: _Pl. 157._ Silver Fir.] [Illustration: Silver Fir. A, cone.]