that ruptures at the apex. The needles are then shed after the scattering of the spores. On the Continent Chr. ledi, also heterocious, grows on Ledum palustre, and likewise produces a similar disease on Spruce foliage.

(d) The Pucciniaceæ are another group belonging to the family of rusts, but are of far more importance to the farmer and the fruit-grower than to the forester. The teleutospores are stalked, and germinate with a typical promycelium. This group comprises several genera and many species, which almost all infect shrubs and weeds, and which are partly autacious and partly heterocious.

The Puccinia genus includes P. graminis, which produces its acidia on the leaves of Barberry (Berberis), and then appears destructively as the rust on wheat (for which reason the Barberry should not be tolerated in hedges round wheat-fields); P. coronata on the Alder Buckthorn (Rhamnus frangula) and P. coronifera on the Common Buckthorn (Rh. cathartica), both of which produce rust on oats; and P. pruni spinosa on the leaves of the Blackthorn or Sloe and other species of Prunus, whose alternative host-plant has not yet been discovered.

The Gymnosporangium genus perenniates in the foliage and twigs of Juniper, on which the teleutospores (no uredospores are formed) break out in small cones in spring, and become large jelly-like pustules during wet weather. The pycnidia and the acidio, which are enclosed in a strong thick envelope (pseudoperidia), opening either pencillately or like a gate (and thus forming the characteristic form Roestelia), ripen in summer and autumn on the leaves of Apple- and Pear-trees. There are five European species, of which the two commonest are Gym. juniperum and Gym. tremelloides, which both occur on the Common Juniper. The former breaks out as pustules on the foliage and on spindle-shaped swellings all round the twigs, then develops the alternating form of Roestelia cornuta on the leaves of the Mountain-Ash; while the latter causes similar swellings on twigs (but only on one side of them and not all round), where thick brown spore-pustules break out and then turn yellowish-brown, before rupturing and producing the alternating form of R. pencillata on the leaves of the Service-tree (Sorbus aria), and often also in large numbers on the foliage of Apple-trees. Gym. clavariaforme causes similar one-sided swellings on the twigs of Juniper, and produces yellow cone-like beds of teleutospores, which produce the alternating form of R. lacerata on Hawthorn foliage; while Gym. sabina infects the foliage of other species of Juniper, and then becomes R. cancellata on the leaves of Pear-trees.

II. Hymenomycetes.

This family belong to the higher class (Autobasidiomycetes) of the Basidiomycetes, and is characterised by having unseptated basidia, which usually have four filaments (sterigma) at their apex, each of which produces one basidiospore. Except in the genus Exobasidium-one species of which, E. vaccinii, produces red and white blisters on the Cowberry (Vaccinium vitis-idea), and another, E. rhododendra, similar blisters ("apples") on Rhododendrons - the extended hymenia occupy definite, free-lying, characteristic positions, and have mostly sporophores of striking shape, such as the well-known mushrooms and "toad-stools." Conidia and chlamydospores are only produced in comparatively few cases.-This family includes a great many saprophytic fungi to be found in dead wood, but those here described below are wound-parasites which enter and entirely decompose and destroy the woody tissues, making the trees useless as timber. Three of these (Trametes pini, Fomes annosus, syn. Trametes radiciperda, and Agaricus melleus) are very destructive in woodlands.

In the genera Trametes, Fomes, and Polyporus the substance of the sporophore, which is usually bracket-shaped, unstalked, and growing out from the side of its host, is firmly connected with the hymenium formed of a compactly interwoven mass of narrow tubes.

In the genus Trametes the substance between the intervowen spore-tubes of the receptacle is the same as that of which the cap is made; whereas, in the genera Fomes and Polyporus it is different (see pp. 182, 184). In all these three

genera the spore-receptacles are bracket-shaped and sponge-like, whereas the genus Agaricus differs from them in its characteristic cap (pileus) forming the typical mushroom or "toad-stool."-Trametes, Fomes, Polyporus, and Agaricus are the fungi which produce "red-rot" and "white-rot" in trees. When the cell-wall substance (cellulose) is dissolved by a ferment in the fungus mycelium, a residuum of tannin, &c., is left behind, which oxydises and becomes reddish-brown ("redrot"); but when the fungus ferment merely decomposes the lignine deposits on the cell-walls and leaves the cellulose undissolved, the decomposed wood is whitish ("white-rot"). The best way of preventing attacks of such wound-parasites is to tar wound-surfaces after pruning, &c.

(a) The genus Trametes.

1. Trametes pini, the Pine Stem-rot Fungus. This disease (Fig. 181) chiefly attacks and causes rot in the stems of Pines about 40 years old or more, though it also infects Spruce, Larch, and Silver Fir. Younger trees are less liable to attack, as wounds on them in the shape of broken branches, &c., are usually closed up by

outflow of resin before the fungus can obtain a firm foothold; whereas on older trees, which have already begun to form heartwood, this natural protection is diminished.

About

Fig. 181.

natural size.

Section showing the rot caused in a Pine-stem by
Trametes pini.

a. Bracket-shaped sporophore issuing from the side

of the stem.

Life-history.-The spores germinate on wound-surfaces or wherever green branches have been recently broken off and are not yet occluded with resin. The hyphe enter, destroy the cell-walls of the woody tissues, and force their way into the heart of the tree. The mycelium extends up and down the stem, and especially in the spring zone of the annual rings, so that ring- or heart - shakes are formed, extending from the crown downwards. The rapid increase of the mycelium soon produces rot in the heartwood, while the sapwood usually remains uninfected. The diseased wood first becomes reddish-brown, then white patches appear here and there, wherever the ligneous substances consisting of cellulose become dissolved, and sometimes the tree becomes completely hollowed. The mycelium next issues from branch-holes only in Pine and Larch, or else both from branch-holes and direct through the bark in Spruce and Silver Fir, and forms a brown, corkywoody, bracket-shaped receptacle or sporophore. In Pine and Larch the decomposition of the woody tissue proceeds only as far as the sapwood, where it is stopped by the formation of a hard layer of resin. In Spruce and Silver Fir, however, which have no well-defined zones of heart and sapwood, and in which there is no special resinification at this particular part, the wood rots right through to the bark. The brown, corky-woody, bracket-like spore-receptacles which thus appear outside the infected stems show concentric ridges, varying up to about 10 inches in breadth, and sometimes live for about 50 years.

Prevention and Extermination.-Infected trees should be at once thinned out.

This not only helps to prevent the disease from spreading, but allows one to have the use of the timber before the stem becomes rotten and valueless on the disease spreading down from the crown of the tree. Large branches of conifers should not be pruned without at once giving the wounds an antiseptic coating of coaltar, or of a mixture of 1 gill paraffin to gallon coal-tar.

(b) The genus Fomes.

The genus Fomes differs from Polyporus in having its bracket-shaped sporophore corky-woody from the outset, and in forming regular concentric layers of sporetubes as it grows older; whereas in Polyporus the receptacle is at first fleshy and tough, and only hardens later on (though in some cases it becomes brittle), and the spore-tubes are never ranged in layers.

1. Fomes annosus Fries (Trametes radiciperda R. Hartig), the Red-rot Root-fungus (Fig. 182), is one of the most destructive diseases in coniferous woodlands. It chiefly attacks the living roots of Scots and Weymouth Pines from about 5 years old upwards, then Spruce and Silver Fir; but it is also found on those of Douglas Fir and other conifers. It is the most

Sporophore of Fomes annosus (Trametes radici perda) on a Scots Pine root.

destructive form of "red-rot," and when once it obtains a foothold in a conifer timber-crop, it spreads centrifugally from root to root. It is sometimes found on the roots of various broad-leaved trees (especially Beech and Birch), but is not then anything like so destructive or so apt to spread epidemically as in conifer woods and plantations. When attacked, young plants, poles, and trees soon show pale needles and stunted shoots (as also in attacks of Agaricus melleus), then they rot near the roots and die suddenly, after which the disease quickly spreads around, and, unless eradicated, makes blanks in plantations and interrupts the canopy in older woods. Wherever a diseased root comes in contact with the roots or rootlets of a healthy tree, infection takes place. The roots then gradually die, and the whole tree rots. The diseased wood first turns violet, then pale brownish-yellow, with black spots here and there which afterwards become surrounded with a white zone. The wood gradually gets lighter and spongier, then hollows become excavated, and the whole rots.

Life-history.-Infection usually takes place in the roots, and, as a rule, comes from the diseased roots of a neighbouring stem, although the spores can easily be conveyed to wound-surfaces on the roots of healthy trees by mice, insects, &c.

The soft mycelium, sometimes transparent, sometimes snow-white, develops beneath the bark and quickly permeates the cambium and the woody tissue of the roots and the butt of the tree. The cell-walls are penetrated and destroyed by masses of mycelial filaments, and the whole root-system often looks rotten and damp. This rottenness soon spreads up into the stem and penetrates the wood by the cambium and the medullary rays-except in the Scots Pine, in which morbid resinification is at once induced to such an extent as to hinder the mycelium from growing further upwards, and thus to confine the rot to the butt of the stem. Destroying the living cells as it spreads, the mycelium quickly penetrates the wood of the infected roots and then extends more slowly into the bark, where it forms between the bark-scales long, thin, tissue-paper-like mycelial strands with small nodes where they protrude between the bark-scales. The small yellowish-white pustules protruding from the bark-fissures are a secondary symptom indicating that the disease has already obtained very complete possession of the tree infected. The mycelium can now spread from the diseased roots and carry infection to all the neighbouring plants or trees. The small, glossy, yellowish-white, grape-like masses of sporophores, appearing mainly on the roots, or at the base of the stem between the bark-scales, afterwards turn chocolate-brown above and snow-white below, and form thin concave woody cushions which unite with similar adjoining groups, and sometimes form large flat incrustations or bracket-shaped excrescences about 12 or 15 inches across. But mould-like masses of conidia can also be produced where the mycelium comes out into free air.

Prevention and Extermination.-Direct infection by spores can hardly be prevented. When the disease has broken out, the best that can be done is to grub up and remove all diseased material before the sporophores are produced, and to plant broad-leaved trees in place of the conifers lifted. Infected patches can be isolated by means of narrow trenches; but this usually leads to prolific development of sporophores on the roots cut through, so that this measure is only to be recommended where the sporophores can be collected and burned before they can ripen and scatter their spores.

2. Fomes igniarius, the White-rot Fungus, is one of the commonest woundparasites producing "white-rot" in most kinds of broad-leaved trees, but especially in Oak, Willows, and fruit-trees. At first the infected wood turns brown, then yellowish-white. The sporophores are hard throughout, round, and tubercular, then form a cap or turn bracket-shaped, and measure up to about 10 or 12 inches across. At first they are yellowish-brown and felty, but afterwards turn blackishbrown and smooth with concentric ridges. The openings of the spore-tubes are cinnamon-brown in colour. It owes its specific name to the spongy sporophore having formerly (as well as F. fomentarius) been much used as tinder in the old days of flint and steel.

3. Fomes fomentarius is a wound-parasite on the Beech chiefly, but also on Oak and Elm, where its broad leathery mycelium, penetrating the wood radially, also produces "white-rot." It forms large, hoof-shaped, russet-brown or greyish sporophores, sometimes over 3 feet long, with a hard upper crust and soft spongy inner tissue (formerly prized as tinder).

4. Other species of parasitic rot-producing Fomes (all of them wound-parasites) include F. connatus on Maple and Sycamore, with white or grey corky sporophores ; F. fulvus, producing "white-rot" on Aspen, Hornbeam, and Plum-trees, with large, smooth, yellowish-brown sporophores, turning grey and fissured; F. marginatus, mostly on Beech, and also on Oak and Birch, producing large, flat, smooth or grey-downy, concentrically ridged sporophores, with variegated edges and leather-coloured interior; F. salicinus, often very destructive to Willows and Osiers, with smooth, hard, cinnamon-brown sporophores, often more or less inverted, which change to grey. F. pinicola is another

species found on dead portions of Pines, Spruce, Firs, Birch, and Cherry-trees, and probably also growing parasitically on them. It has large, hoof-shaped, corky-woody sporophores, yellow at first, then blackish, with a vermilion-red edge, and whitish internally.

(c) The genus Polyporus.

1. Polyporus sulphureus is a wound-parasite producing "red-rot" on Oak, Willows, Poplar, and Birch chiefly, but also on other broad-leaved trees, and on Larch and other conifers. It is also a common saprophyte in orchards. The sporophores appear annually, at old branch-holes or on the stem, as large, fleshy or cheese-like, bright sulphur-yellow or reddish-yellow receptacles of different forms, and varying up to over 2 feet long.

2. Polyporus vaporarius is another wound-parasite which produces "red-rot" in Spruce, Scots Pine, and Silver Fir. It is also destructive as a saprophyte in decomposing and rotting timber lying in the woods (much in the same way as Merulius lacrymans, which is seldom found living parasitically on trees in the woods; but the mycelium of the latter soon changes from white to grey, while that of P. vaporarius always keeps white). Its sporophores are not bracket-shaped, but so inverted that the hymenium is above; and they form flat, thin, white incrustations on the bark of the trees infected.

ever,

Other parasitic Polypori which produce red- or white-rot on living trees include(a) Producing “red-rot”—(1) P. betulinus, a wound-parasite on Birch, which annually forms fleshy white sporophores mostly of horse-shoe shape, which afterwards turn corky and have a thin brownish skin and short spore-tubes. (2) P. sistrotrematis (syn. P. mollis R. Hartig; P. Schweinitzii Fr.) on Scots and Weymouth Pine. In this case, howthe cellulose is decomposed as well as the lignine (see remark about "red-rot" on p. 181), and the diseased wood, which smells very strongly of turpentine, gradually becomes rotten. It annually forms orange-yellow, soft, spongy sporophores, sometimes bracket-shaped though mostly in the form of a wine-funnel, and with short thick stalks, but afterwards becoming dark-brown and corky. The mouths of the spore-tubes are broad and sulphur-yellow or greenish (turning to brown later), but when touched they change to deep-red.

(b) Producing "white-rot"—(1) P. Hartigii (P. fulvus), common on Silver Fir, and especially near canker-spots, and occurring also on Spruce, produces sporophores reddishbrown or ashy-grey above and yellow-brown at the mouths of the spore-tubes. On the stem these sporophores are bracket-shaped, while on the branches they are more or less irregular in form. (2) P. dryadeus produces yellowish and white irregular stripes of decomposition in the dark heartwood of Oak-trees, and annually forms large sarcous sporophores up to over 18 inches broad, which afterwards turn corky and rusty-brown, and have deep ridges and furrows on their upper surface. They soon rot after the ripening of the spores. (3) P. hispidus is common on Apple-trees, and also occurs on Ash, Elm, and Plane. It annually forms soft, spongy, cushion-like sporophores up to about 10 inches broad, rustybrown above and yellowish below. (4) P. borealis produces a peculiar kind of "whiterot" in the Spruce. Small transverse holes are produced in the spring zone of wood and are filled by the mycelia, and the whole of the wood finally decomposes in small cubes or rectangles. The sporophores are formed annually, and appear as white, sarcous, watery, cushion-like or bracket-shaped excrescences, usually growing in clusters and overlapping like the slates on a roof, and about 2 to 3 inches broad and 2 inches thick, which have an unpleasant smell. (5) P. squamosus often infects various kinds of broad-leaved trees, and annually produces semicircular or kidney-shaped sporophores, at first toughly sarcous and later corky, with stalks placed excentrically or at one side, yellow above and brown-scaled, often clustered in masses ranged like roof-tiles. (6) P. lævigatus infects the Birch, and produces inverted, thin, brown, rough leathery sporophores, with a felty light-brown edge at first, but afterwards forming an incrustation which loosens itself from the host-plant.

"White-rot" is, however, also caused by two other parasitic fungi belonging to other families of this group, Hydnum diversidens (Hydnacea) and Stereum hirsutum (Thelephoriacea).