tinguishable, by the numerous dark-red globular sporophores on the cankerous spots, from any other diseased condition caused by sun-burn, frost, or plant-lice; but they are very minute and can only be found by careful examination.

Life-history. This fungus grows only as a parasite, effecting its entrance at wounds, such as those made by insects, frost, hail, &c. It attacks crops of all ages

from young poles upwards, and is even found on 1-year-old shoots. The mycelium lives chiefly in the bark, killing the infected portions, and gradually extending its infection. Canker-spots then arise as the tree each year tries to cicatrise the dead parts, which gradually increase in size. The conidia-cushions are white, and the perithecia red.

The infection often begins at the fork of young branches, from which the

mycelium spreads up and down the stem, turning the diseased wood brown in Beech and black in Ash. The canker deepens with the growth of the mycelium, and as the edges become raised by the repeated attempts at cicatrisation, a hypertrophic condition follows, resulting in spindle - shaped excrescences along the cankered part. The stem and branches gradually become more and more cankered, till the pole or tree is killed outright.

Prevention and Extermination.-Infected saplings, poles, or trees should be thinned out; and during thinnings, or when felling and removing trees from areas regenerated naturally, care should be taken to avoid making wound-surfaces by injuring the bark on the poles or trees left standing as the crop.

"Prevention and Remedies recommended for orchards, where this is the most destructive canker on Apple-trees, are as follows:-Young branches that are attacked should be cut off, as they are certain to be girdled and killed at an early date.

When thick branches are diseased all the wounded parts should be cut away and the cut surface luted with clay or protected with a coat of gas tar. If the disease has spread from the original point of infection, and appeared at the surface in other places, the branch should be cut off.

It is very important that grafts should not be taken from diseased trees, as parts that appear to be sound may contain the fungus in their tissues.

The white stage of the fungus can be killed by applying with a brush a solution of sulphate of iron-1 lb. to a gallon of water. This mixture will also destroy lichens and moss growing on the trunk and branches."—(Board of Agriculture Leaflet, No. 56.)

2. Nectria cinnabarina, the Coral-spot or Horse-Chestnut Fungus, is one of the commonest saprophytes on dead branches of broad-leaved trees; but it is also parasitic on the buds, twigs, and branches of Horse-Chestnut, Lime, Maple, Sycamore, and Elm, destroying the sapwood in rings and killing the parts above those infected. (See also Agricultural Leaflet No. 115, Coral-spot Disease.)

Appearance and Life-history. On parts attacked saprophytically great numbers of small brick-red conidia-cushions break out of the bark, upon which the vermilion and dark-red perithecia appear during the autumn and winter. But the mycelium can, as occurs most frequently on Horse-Chestnut and Elm, extend parasitically from wound-surfaces into living branches. It soon spreads quickly in the vessels of the woody tissue, and kills the branches by preventing the upward flow of the watery sap. The fungus then decomposes and consumes the starch contained in the wood-cells, and leaves behind a greenish substance which soon causes the wood to turn black and discoloured.

Prevention and Extermination.—Dead or damaged branches should be pruned, and the wound-surfaces tarred; and all infected parts should be cut off and burned. These protective operations should be carried out before the spores scatter in autumn and spring, when the risk of infection is greatest. Spraying with caustic soda solution in winter is also recommended.

3. Nectria curcubitula, the Spruce-bark Canker (Fig. 173), occurs chiefly as a wound-parasite on young Spruce poles, but is also found on Silver Fir, Pines, and Larch. It is common in Britain, though generally only as a saprophyte on dead branches. It is prevalent in damp frosty localities, where twigs nipped with frost or injured by insects, hail, &c., enable it to effect its entrance in weakly young trees of 3 to about 15 feet high. On young trees in vigorous growth it remains saprophytic, the progress of the disease being stopped and a corky layer being formed that cuts off the diseased tissue, which then dries and is shed. But in weakly young trees the canker is able to extend, killing the cambium and penetrating the sapwood.

Appearance and Life-history.—The first signs of the disease are bleaching of the needles, and drying and browning of the bark and cambium, especially near wounds caused by insects, &c. The mycelium spreads quickly in the bark, especi

ally throughout the sieve-tubes of the phloem, and the development of the fungus is mostly confined to the winter period when the tree rests from active vegetation. It kills the bark, and often also the wood of young twigs and stems, so that the leaders are often killed on plants in young Spruce plantations (mixed as well as pure). When the disease encircles the stem, the crown and often the whole plant dies; but if a strip of bark remains sound, active vegetation of the young tree can proceed, and the cankered spot may in course of time become completely cicatrised. The sporophores can only develop when the dead bark is always kept moist. White and yellow conidia-cushions are first of all formed about the size of a pin's head, and on these numerous groups of scarlet concave perithecia containing the tube-spores are afterwards produced. So long as the host is in vigorous growth the fungus cannot penetrate beyond the resting parts of the bark, as the living cells of the cambium grow and divide normally; but if unsuitable soil or situation, or injury of any sort has predisposed the young tree to disease, the cortical tissues, the cambium, and even the sapwood are attacked, so that the upward flow of water is stopped and the whole of the part above the infected place dries up and dies.

Prevention and Extermination.-Young plants or parts of plants attacked should, during the autumn and early winter, be cut off and burned, as the spores easily scatter when infected parts are shaken; pruning-shears should be used whenever practicable, and care taken to avoid scattering the spores.

II. Sphæriaceæ.

This family is characterised by dark perithecia, which either stand quite free on the conidia-cushion or are surrounded by a thread-like layer; but they are never embedded in a true cushion-like stroma.

1. Trichosphæria parasitica, the Silver Fir Needle-blight Fungus, is a very common and destructive parasite, which very often in damp localities attacks thriving young poles and the lower branches of 20- to 40-year-old Silver Fir, and sometimes also Spruce and Tsuga. It does a good deal of damage on the Continent in natural regenerations and thick young plantations. When twigs are attacked the needles turn brown, become loosened from the twig and hang down, but are prevented from falling by the fine mycelial threads. The mycelium perenniates, and trees attacked never shake off the disease.

Appearance and Life-history.-The thin colourless mycelium is generally found on the lower side of the last sprays of Silver Fir, where it forms numerous white pustules on the two silvery grooves along the needles. As the needles turn brown and hang down, the pustules also turn brown; and about November small, round, blackish-brown, hairy perithecia are formed, containing dirty-grey spores which scatter and germinate on Silver Fir foliage. But besides scattering myriads of spores to spread the infection, this fungus never, before killing the young tree attacked, relaxes the hold it once attains on it. The mycelium hibernates on the lower side of the spray and needles (which generally die during the year following infection), and extends to the new shoots flushed in spring, attacking first the needles on the older spray that may have escaped in the previous year, then killing at once the needles not yet fully developed at the base of the new shoot, and afterwards gradually infecting those on the middle and upper portions of the twig. Sometimes young shoots are in spring thickly covered with mycelium and all the leaves are dead, so that the whole twig dies off. The black perithecia which appear on the small, white, and afterwards brown, conidia-cushions on the lower side of the leaves can hardly be distinguished by the naked eye. They have tufted wisps of hair on their upper half, and the asci contain eight bright-grey 4-celled spores capable of germinating immediately.

Prevention and Extermination.—Infected twigs should be carefully pruned so as not to scatter the spores, and should be burned.

2. Rosellinia quercina, the Oak-seedling Fungus, attacks and kills the roots of 1 to 3-year-old Oak-seedlings, more especially in seed-beds and nursery-lines during damp warm spring and summer weather; but plants are still liable to attack up to about ten years of age. The terminal leaves of infected plants gradually fade and dry up, and then this drying-up process is continued downwards.

Appearance and Life-history.-The infected tap-root becomes covered with finely-woven mycelial filaments near which the bark-tissue turns brown; while small, round, black pustules about the size of a pin-head appear on the tap-root, and especially where the first tiny side-roots branch off. From these small black pustular sclerotia numerous fine thread-like rhizomorphs (rhizoctonia) proceed, at first whitish then turning brown, which surround the roots and extend throughout the soil, spreading infection from root to root, very much in the same way as Agaricus melleus, see p. 185), while the white mycelium sometimes also grows above ground among the grassy soil-covering. By means of these small black pustular fruits (sclerotia) the fungus perenniates and hibernates, retaining vitality from year to year, and also outliving periods of summer drought in which any ordinary form of mycelium would perish; and when the atmosphere becomes damp again these sclerotia develop a thick, whitish-grey, mould-like mycelium, which in turn again produces numerous brown rhizomorphs (rhizoctonia).

As the tap-roots of the Oak-seedlings are protected by an outer corky layer against infection, the mycelial filaments have to effect an entrance through the less protected side-rootlets, whence they can extend unhindered into the whole of the inner tissues of the roots and stem. Infection can also, however, be effected by the conidia produced by the mycelium above ground, as well as by the spores scattered from the black pustular sclerotia developing on the surface of the soil or on the stems of the diseased seedlings. These different kinds of mycelia penetrate the living bark through the tips of the rootlets or through the lenticells, especially at the base of the side-rootlets, where small swellings appear at the infected parts, from which mycelial filaments extend to the inside of the roots during damp, warm, favourable conditions of soil and atmosphere. The bark-cells become filled with thick mycelium (pseudoparenchym) and then die, and finally the mycelium extends right into the centre. The roots soon turn black, and then assume the characteristic look of white-rot. The conidia formed in summer are borne on whorled branching sporophores, entirely different in appearance from the round black perithecia produced either on the surface of the infected rootlets or in the vicinity of the rhizomorphs rising to the surface of the soil.

Prevention and Extermination.-Diseased plants should be at once removed from the seed-beds and nursery-lines and burned. Young plantations or parts of natural regenerations infected should be isolated by digging narrow trenches about 1 foot deep all round them, to prevent the rhizomorphous mycelium spreading subterraneously.

White Root-rot (Rosellinia necatrix) attacks wild cherry-trees and crabs in woods and hedgerows. (See Agricultural Leaflet No. 64.)

3. Sphaerella laricina, the Larch Leaf-shedding Fungus, has on the Continent proved a very destructive disease at low elevations. About the end of June (those attacked by Chermes even earlier), or in July, the needles become spotted with brown and soon fall off. In wet years most of the foliage is shed by August; but in dry seasons the disease only occurs in low-lying damp

situations where Larch is interspersed among evergreen conifers, on the foliage of which the infected Larch-needles of the previous year have remained hanging, and have produced ascospores. At low elevations the Larch thrives best when underplanted with, or interspersed among, Beech, because the infected Larch-needles are shed before the Beech-leaves, and the latter completely cover the former and prevent the spores being scattered.

Life-history.—The mycelium lives intercellularly. The conidia-cushions break through the epidermis of the infected needles still hanging on the twigs, and appear as tiny black spots with sausage - shaped conidia, which are very liable to be washed off during rainfall, and then quickly spread the disease during wet weather. These small black dots are minute spherical cavities (sphærella) sunk in the leaf-tissue and surrounded by a dark cellular investment. In the following spring the perithecia and isolated pycnidia appear as still smaller black spots in great number on the fallen needles.

Prevention and Extermination can only be effected by cutting out and removing infected poles or trees, and burning the diseased foliage.

4. Sphærella taxi attacks Yew foliage in the S. W. of England. The leaves infected show numerous small black spots, which are little spherical cavities in which the asci are produced. As Yew-needles have a hard and firm epidermis, when spores land on them and germinate the germ-threads can only enter by the stomata. The disease is therefore slow in spreading, but twigs and branches attacked should be pruned off and burned.

5. Aglaospora taleola sometimes attacks the branches and stems of young Oaks as a wound-parasite, and then spreads and produces a destructive cankerous disease, causing the smooth bark to die and burst open, after which cicatrisation gradually takes place. The mycelium also enters the wood, turning it brown superficially. On the diseased bark, which is thrown off later, the perithecia are grouped together with long necks under the periderm and perforating this, but only the mouth of the perithecium extends above it. The asci have eight 2-celled spores with thread-like appendages. But besides these, 1-celled, sickle-shaped conidia are also released from the quasi-stroma, near the mouth of the perithecium.

6. Ceratostoma piliferum is a saprophyte which occasions bluish discoloration in coniferous timber (especially Pine). The brown mycelium enters into the dead stems from without, and quickly spreads throughout the sapwood, but does not usually penetrate into the heartwood.

III. Hypodermataceæ.

This family, the Scurf-Fungi, has flat or elongated sporophores, called apothecia (like those of the Discomycetes), whose tough, leathery, black envelope is intergrown with the substratum-layers, and bursts lengthways when the spores are ripe. In damp weather the edges of this fissure open wide, but in dry weather they close again after scattering the spores. The closed apothecium is filled with densely-packed paraphyses, between which the 8-spored asci are embedded. The spores are mostly thread-like, with a gelatinous membrane which expands with moisture. The apothecia are produced on the dead tissues some little time after the mycelium has killed these; but small 1-celled conidia can also be formed in pycnidia. Two genera, Hypoderma and Lophodermium, attack trees.

In the genus Hypoderma the spores are not long and thread-like, but are always 2-celled when ripe, and much shorter than the tubes.

Hypoderma strobicola kills the needles and young shoots of the Weymouth Pine, sometimes entirely defoliating large clumps of plantations. The needles turn brown in summer, then the apothecia appear as narrow black lines, and the foliage is shed in winter. The ascospores are ovally elongated.