There is a parasitic Lichen which often proves very injurious to fruit-trees in old orchards. It is generally of a lightish-grey colour, and when fully established upon the tree, gives it rather a grand and imposing appearance, especially in winter, when the foliage has departed from the branches. I know of no writer who describes its general appearance so graphically, yet so truly, as Longfellow, in the introduction to his beautiful poem of "Evangeline," when, speaking of the primeval forests of Acadie, now Nova Scotia, he says -

"This is forest primeval. The murmuring pines and the hemlocks, Bearded with moss, and in garments green, indistinct in the twilight, Stand like Druids of old, with voices sad and prophetic, Stand like harpers hoar, with beard that rests on their bosoms".

It generally makes its appearance upon the trunk of the tree, from whence it gradually spreads itself until every branch thereon becomes hoary and grey by it, unless means be taken to destroy it. It will also be observed that the portion of the tree which is most exposed to the storm will be the first to suffer thereby; and even although the whole tree have less or more of it, the side to the storm will most abound. This Lichen belongs to one of the five classes into which they have been divided; viz., the Homothalami, which means that the apothecia or receptacle is altogether formed of, and is the same colour as, the thallus or frond. This class is subdivided into many varieties, but the one to which I refer is an Usneas, but what one I have some difficulty in determining.

The Lichen belongs to the lowest and most simple form of vegetation, the Fungi tribe alone excepted. Some writers appear to think that this parasite does little or no injury to the tree upon which it grows. Of this, however, I am very sceptical; at all events, it is not to be found upon a young healthy tree, so that if it really does not do harm, it certainly is an indication of want of health in the tree. "Lichens," one writer tells us, "exist exclusively on atmospheric supplies, requiring only air, sunlight, and some degree of moisture for their support." This no doubt is certainly true, but the atmosphere in a season of protracted drought certainly cannot supply that "degree of moisture necessary for their support" without the aid of the tree. Let the season of drought be ever so protracted, it will be noticed upon the raising of a portion of this parasite from the branch of the tree that a certain amount of moisture lies underneath. Let us therefore take into consideration the dryness of the atmosphere, the burning rays of the sun, and the thinness and the permeability of the Lichen, and what other conclusion can we arrive at regarding the moisture to be found beneath it, than that it has been derived from the branch upon which it lodges ] It matters not how much horticulturists be divided in opinion regarding its effects upon fruit-trees, all are at one that it should not be there.

It consists of a dry scaly crust having neither roots, stems, nor branches, yet nevertheless attaches itself with great pertinacity to the seat of its existence. It extends itself over the branch by a multiplication of its thalli, which are of a curled appearance, resembling leaves, and performing the same functions. Being a cryptogamous plant, it bears no flowers, but around the edges of the thalus it abounds in spore-cases, which are either growing from or imbedded in its surface. Although in some cases the Lichen does not spread very rapidly, yet in others it does so with amazing rapidity. This altogether depends upon the state of health enjoyed by the tree. If the tree should be in a very delicate state of health, the spread will be all the more rapid, as these spores when ripe get shifted by the wind from the parent plant to other portions of the tree, there in due course of time to become independent plants. Laying aside altogether the fact whether or not the presence of this Lichen is injurious to the tree by draining its life-blood out to support the parasite, there is the undeniable fact that its presence prevents to a greater or less extent the free admission of light and air, as well as that due amount of respiration which is so necessary for the health and wellbeing of the tree.

It is a well-ascertained fact, that wherever a tree is attacked its usual vigour is soon diminished, the growths become more weakly year by year, and in the end the growth comes almost to a stand. Not only is this the fact, but as a natural consequence the fruit becomes less in quantity, smaller in size, often deformed in shape, and always of an inferior flavour. It is therefore the interest of the cultivator to ascertain the cause of its presence, so as to be able in his future management to obviate further injury from it, and endeavour as far as possible to find out a remedy for those already suffering.

I have failed to find that any of our leading horticultural writers have given any attention to this enemy of fruit cultivators. Many and various are the private reasons I have heard assigned for its presence, many of them very plausible, some of them very absurd. The conclusion which, from observation, we have arrived at concerning it is, that trees under good management and in a healthy state always escape; whereas trees, especially old trees in bad health, are always attacked. Now what has been said in former papers regarding the keeping of a tree in health, must at once force upon the reader the reasons which we assign for its presence. A cold and wet soil or subsoil, into which the roots have penetrated, and which provides food wholly unsuited for the tree, is the root and origin of this evil as well as canker. And did the fact never strike the cultivator, that where the one was present the other is seldom if ever absent? The fact is, in all our experience, and that of several other gardeners to whom we have spoken upon the subject, the one is the handmaid of the other. If this be the fact, and there is little doubt of it, what will be a cure for the one will also be a cure for the other.

It matters not how much two diseases may be at variance in their general aspects; if to the same causes the two are to be attributed, then the same means will be sure to cure both. To cure any disease, or to counteract any effect, we must work in direct antagonism to the causing force or power. The first duty, therefore, of the cultivator, is to have recourse to thorough drainage, so that no superabundance of moisture may lodge about the roots. Thereafter let him raise and examine his trees in the manner already directed in a former paper, having them thereafter replanted in soil more congenial to their wellbeing; after which, let all the Lichens be thoroughly scraped off with a blunt-edged instrument of some sort, or, what is better, on a wet day or dewy morning in winter, when the tree is at rest and devoid of leaves, let a quantity of lime (quicklime) be procured, which may be thrown with a shovel up through the tree until a thorough coating be obtained all over, and the result will be that in a short space of time all the Lichens will be removed from the trees.

This is the more speedy way of getting clear of the enemy, but it is not absolutely necessary, for as a rule the fresh vigour which will be thrown into the tree by root-pruning, etc, will have the effect of throwing off the old bark as well as the Lichens. There are various other Lichens and Mosses which attack fruit-trees, but the one already described is the most formidable and best known. I have therefore selected it for illustration, but may add that the cause and cure in every case are exactly the same.

I have dwelt at much greater length upon this portion of my subject than at first I had anticipated; my reason for doing so is, that it is a point in fruit cultivation which has received little attention, and, so far as I am aware, has never been discussed by any of our horticultural writers. Having thus disposed of the diseases to which the Apple is subject in this country, I would now draw the attention of the reader to some of the more formidable of the insect enemies with which we have to contend. First of all we would notice the American blight, or woolly bug, as it is commonly called. Various entomologists have given it various appellations, but it is generally known to scientific students as Aphis lanigera, which is the name given it by Linnaeus, the Swedish botanist. Its common name would indicate that it was an importation from America, but this is universally denied by all American writers upon the subject. Mr M'Intosli in his Booh of the Garden says "that this insect appears indigenous rather to France and the north of Germany than to America, from which country it has been erroneously supposed to have reached us." Be this as it may, it is the most destructive of all the insects which attack the Apple, and is at the same time by far the worst to thoroughly eradicate.

Not only does it feed upon and destroy the wood of the tree in summer, but in winter it descends to feed upon and destroy the roots. In early summer it may easily be detected upon the wood of several years' growth, as well as the stem and stronger branches, by its white woollylike appearance. When it attacks the wood of two or three years of age, it often perforates the bark and raises little excrescences about the size of a large pea, which, when broken, appear to contain thousands of eggs or little insects. If not attended to, the tree will soon lose vigour, and ultimately succumb to the evil power of its little enemy. Different authors recommend different cures - as, for instance, Mr M'Intosh recommends first "the washing of the parts affected by a solution of sulphuric acid, in proportions of 3/4- oz. by measure to 7 1/2 oz. of water, applying the liquid with a piece of sponge tied to a piece of stick, or by a small soft painter's brush." Or again he recommends "spirits of turpentine, strong whisky or gin, applied to the patches infected." On the other hand, Mr Thomson recommends "scrubbing with soap-suds, and then painting with lime-water or washing with tobacco-water, soap-lees, vinegar or sulphuric acid diluted with water, as well as painting with clay." Any or all of these may prove a thorough antidote, but from experience I cannot speak of them.

I can, however, recommend a cure which I have every confidence in, and which from experience I can recommend as thoroughly effective. To Mr Rose, gardener to her Majesty, I am indebted for the receipt; and I trust I may not break confidence with him in thus giving to our professional brethren, what I have not the slightest doubt is one of the best, if not the best, cure extant for the bug. To one part of spirits of tar, one part turpentine, must be added two parts of train-oil, which must be well mixed, and have added either soot or clay to give it consistence. Let this be applied to the parts affected, and to them only, with a painter's brush, rubbing it well in. By going over the trees thus three or four times during the course of the season, the likelihood will be that the whole colony will be extirpated, at all events the second year will be sure to do it. It may be as well, however, in winter, to remove the soil for a few inches deep around all trees affected, so that, should any have escaped detection in summer, they may have a chance of being entirely removed in winter.

James M'Millan.

(To be continued).