Epiphytes (Gr. upon, and to grow), vegetable parasites found upon man and other animals. Those which grow within the cavities of the same are called entophytes. As no definite line can be drawn between the two, and as some species belong to both classes, they will be considered together in the present article. It is only of late, and since much attention has been given to the study of cryp-togamic botany, that the full nature and importance of the diseases created by many of these growths have been recognized, and the belief in their spontaneous generation been given up. They all belong to the fungi and algae, but we are not yet sufficiently advanced in our knowledge of cryptogamia3 to attempt any minute classification, or to distinguish between these two orders. Robin and Kuchen-meister divide them according to their supposed place in the vegetable kingdom, while Virchow and his followers classify them into those really pathognomonic of disease, and those accidentally occurring in it. For this last arrangement the two following conditions are necessary, viz.: the constant occurrence of the parasite in the disease, and the positive result of inoculation.
There are some who say that even this is not enough, and that the fungus may carry the matter of contagion attached to itself, and that this propagates the disease. Schonlein throws out such a hint with regard to animal parasites when he advises our cleaning the itch insect with brush and bath before proceeding to inoculate; and Clemens of Frankfort asks: "If we were to find constantly in the vaccine matter one and the same fungus, by the transportation of which new variola existed, which should we call the true inoculating matter, the fungus attached to the lymph, or the lymph attached to the spores?" The dwelling places of the cryptogamiae seem as universal as their growth is simple. Deep under the sea are beds of algae; within the bowels of the earth they may be found; the air we breathe contains them, and the winds waft them from pole to pole. They form the chief means of resolving dead matter into its original elements, and are present and are gone with a rapidity inconceivable. No wonder that men believed in the spontaneous development of these forms, for their appearance in certain situations seems otherwise inexplicable.
The animal parasites live mostly on the living tissues of man or other animals; with the vegetable the reverse is generally the case, and it is those parts already decomposed or diseased which form their chief support. They usually attack, or better succeed in establishing themselves upon, parts not intimately connected with the system and superficial, and therefore less able to resist their influence; or else they attend upon long disease, when the strength of the body is already wasted. This cannot be said however of every species. The character of the soil exercises an important influence over their growth, and may in fact change it entirely. Indeed, we can hardly give any general rules; for some affect an acid nutriment, others alkaline; some grow upon the outside, where there can be no warmth, others within the heated cavities of the body; some thrive best in light and pure air, others in darkness and carbonic acid; some live in fluid, while others are always found dry. It will be seen then that all these points must be taken into consideration before we attempt to destroy them, and a universal parasite killer is an impossibility, for what is death to one species may be the food of another.
The effect of their presence on man is as various as that of the animal parasites, though less dangerous. When the plant has found its favorite and essential elements for reproduction, it grows at once, be it on the outer surface or within the body. At first the growth may be merely superficial; but soon the vegetative structure, the mycelium, begins to seek nourishment in deeper soil, and its filaments penetrate all tissues, wherever the minutest opening is left for its entrance. The spores or mycelium, by acting as a foreign body, may produce absorption in adjacent parts, and thus make way for their progress inward indefinitely. When once the spores gain admission we may see the same result as when we plant the seeds of larger vegetables in the soil. They send forth their sprouts upward and downward, pushing before them whatever resists their progress. But if in addition to the sprouts we should have our seed increasing by self-division, and to an immense extent, what would follow? What wonder then if this process, carried on beneath the less yielding skin, should lead to inflammation and destruction of the parts? The oidium albicans may become dangerous in an infant by obstructing the oesophagus or glottis. Impaired vision may be caused by the growth of a fungus within the eye.
Atrophy and deformity may result from their presence in the hair and nails. Erosions of the skin, and the inflammation they create, may bring on swelling of glands. Parasites may also prove injurious by irritating the nervous system, as in pityriasis versicolor, or chemically. The vinous fermentation is brought about by the action of a fungus on sugar, by which it is resolved into carbonic acid and alcohol. So too the sarcina ventriculi and the oidium albicans may cause the acetous and lactic acid fermentations respectively. The very decay of vegetable parasites may produce putridity in their masses. We see then that vegetable parasites are able to work a multitude of evils upon mankind, but the extent thereof must be in proportion to the condition and size of the organ affected. Although they may in some instances be as troublesome, as dangerous to life even, as their animal relatives, still we are not so much shocked to have our head covered with the sporules of the favus plant as with pediculi, though both are marks of un-cleanliness, or to know that our stomach is filled with sarcina, as to suspect that a frightful strongylus lies coiled up in our kidney. - Fungi consist of organs of fructification and a nutritive apparatus.
This last is called mycelium, and is made up of threadlike, more or less compacted, elongated cells, which interlace and ! have no intimate connection. It has such an indefinite form, and differs so little in various species, that from it alone we cannot distinguish them. It varies greatly also according to the condition in which it grows, and whether it be viewed damp or dry. It may exist without bearing fruit, as a tree may remain barren in uncongenial soil; but no species can exist without it, though it may be reduced to a very low development when compared with the fruit-bearing system. Subtile forms of mycelium have the power of penetrating to remote parts, and lying dormant for a long time. The reproductive system consists of spores, which are very small, and in some species are enclosed in receptacles. Their number is literally incalculable, and they increase with immense rapidity. They float freely in water, and their walls are very strong, so that they are well calculated to travel far from their birthplace.
Their diminutive size enables them to gain admission into the smallest crevices of the skin or elsewhere, and they are capable of withstanding great extremes of temperature, so that after being kept in a dry state for a long time they are found to possess their entire pristine vitality. The whole plan of their development is still little known, and there is good reason to believe that many of them are imperfectly developed states of other plants, which, if they attained their proper sphere, might present a more complex structure; and when we consider the vast number of forms into which a single germ may develop itself according to the soil in which it happens to grow, their real number may be regarded as comparatively small, and this view is adopted by some eminent dermatologists. Some prey directly upon living tissues, while others destroy them first and induce decomposition, before the proper conditions for their development are attained. The fact of possible inoculation on healthy subjects proves that the presence of some forms at least is the essential cause of the disease connected with them.
The fact that mycelium may exist for a long time dormant, till proper conditions are provided for its further development, will explain the sudden appearance of a fungus in various peculiar situations. In the potato disease, for instance, the botrytis infestans may show itself in a few hours on the freshly cut surface of a tuber, and on microscopic examination we find mycelium traversing the cells in all directions. They grow within nuts and egg shells, in the cavities of tomatoes when no lesion of the walls exists, and are developed within the brains of birds, in the eye and bladder of man, and on globules of milk within the udders of cows. Let any room remain undisturbed for any length of time, and then examine the dust which has collected, and multitudes of vegetable spores will be found. We know not but in each breath of air we inhale, each draught we raise to our lips, are lurking germs which, if they find a proper nidus, may make of us a dwelling place. - Among the most important of the vegetable parasites of man is the oidium albicans, which belongs to the same genus as the fungus which has proved such a destructive pest to the vineyards of southern Europe and Madeira, viz., the oidium Tuckeri. It forms the disease called aphthae, which shows itself on the mucous membrane, generally on the tongue of infants, as a soft, white, pasty, slightly elevated patch.
On the lips, where it becomes dry, it forms dark brown crusts. Its seat is first the upper surface of the epithelial cells, but soon its filaments penetrate deeply between them, and can no longer be removed by art. It is found also in the nose, windpipe, stomach, and intestine. It may occur in persons of every age, but especially occurs in young children and the old, owing to the liquid form of their food, which allows any accumulation in the mouth to remain undisturbed, and to the long sleep necessary to these ages. It is of frequent occurrence also in the last stages of many diseases, when the mucous membrane is covered with nitrogenous, decomposable matter. According to Kuchenmeister, its appearance is due to catarrh of the mucous membrane, which is very common in old age and infancy, and this is without doubt the most frequent predisposing cause. Robin accounts for its presence on the nipples of nurses by the supposed lactic acid reaction produced there, but it is more probable that the disease is transferred thither with the mucus from the child's mouth, and becomes attached by the extension of the mycelium into the epithelium. Oidium has also been found in the nails and on the surface of ulcers. On diphtheria this parasite is found to be a constant attendant.
Whether its presence causes the inflammation of the throat, or is merely the result of a proper nidus offered it by this specific disease, is not easy to determine. In other cases it seems to give little trouble as a general rule, though in very young children it may produce difficulty of breathing and swallowing. The ulceration which is sometimes found is probably caused by the accompanying catarrh. That it is contagious is shown by its rapid spread in large foundling asylums, and by direct experiment. Its general transference from one mouth to another in such localities is easily understood when we consider their customs - the nipple taken from one child and given to another, feeding various children with the same spoon, and so on. How it appears in sporadic cases also is not difficult to explain, believing as we do that it is an ordinary form, which may grow on many substances, and be transported in the form of its sporules in all directions by the air. - The diseases caused by these parasites may be divided into three groups: those of the alimentary canal, of the scalp, and of the skin.
In the first we place the oidium albicans already described, and here too belongs the torula cerevi-sioe, or yeast plant, its near relative, which is met with occasionally in all the fluid excretions of the body. It forms the ordinary cholera fungus in the vomitus and intestinal discharges of this disease, and is often found in the stomach and attached to the walls of the intestine after death. Its usual presence in fermenting fluids has led to the belief that it was the cause of such change, and we know that when added as yeast it acts as a true ferment; but we do not know but that the peculiar chemical change may offer merely the conditions for its sudden appearance and rapid growth. It is another form of the penicillium glaucum. Another plant, found most commonly in the fluid of the stomach, is the merismopoedia (or sarcina) ventriculi, which has been usually placed among the algae. It has been found also in the urine, in the intestinal canal, and in the lungs. Its presence in the stomach of man probably causes no symptoms whatever; it has been cultivated in the stomach of rabbits, and no trouble caused by its presence.
It is supposed to be present most frequently in patients suffering from some gastric disease, organic or otherwise; but this is to be accounted for by the fact that such only vomit, and afford material or stimulus for investigation. If we remove from our teeth the yellowish white deposit which collects after the neglect of the tooth brush for several hours, we shall find by microscopic examination, in addition to the detritus of food, a cryptogamic plant called leptothrix buccalis. It is to be found in all persons, however cleanly they may be, and forms a large part of the tartar which collects about the teeth. It grows with great rapidity after eating sugar, and has been seen in the stomach. Of the parasites of the scalp, the achorion Schoenleinii is most of all to be dreaded, on account of the deformity and disagreeable odor it gives rise to. It produces the disease known as favus, porri-go favosa, or tinea lu-pinosa. The spores first settle upon the epidermis of the head, and send forth the mycelium, which penetrates the hair follicles and finally the whole course of the hair itself. The hair becomes pale and lustreless, breaks easily, and is surrounded at its base by concentrically marked yellow and roundish crusts, which smell vilely, and consist of spores and mycelium.
From one point this fungus may spread over the whole scalp, producing baldness and scars. Fortunately it is of rare occurrence, for a cure is almost impossible. The trico-phyton tonsurans and T. sporuloides also cause baldness when they attack the hair, and the former produces the disease called ringworm, which is so prevalent in asylums for children. The microsporon Audouini likewise attacks the hair, and the M. mentagrophytes the beard. The only vegetable parasite which is found upon the skin alone is the M. furfur, which is the cause of the eruption known as pityriasis versicolor. Several of the above mentioned species may take root upon the skin as well as the scalp, but they never form a well marked disease like the latter. Various kinds of cryptogamiae have been observed within the ear, eye, lungs, and nails, but the descriptions of them are very defective, and we hardly know where they belong. It is probable that they are species of fungi which have accidentally found a favorable place for development. - Man is not the only animal infested by the vegetable parasites. Upon the mammalia it is true that few have been observed, but this remains an almost unexplored field.
Many birds bear them in their respiratory apparatus, especially the owls, which inhabit damp and shady retreats, frequented by fungi. More curious is it to find within the close-shut cavity of an egg mycelium spreading throughout the contents, and changing them by a peculiar chemical action. This rare phenomenon is produced by the admission of spores within the oviduct before the egg shell is formed. Fish are often taken covered with vegetable growths, which impede their motion through the water as the barnacles act upon ships. A great many species have also been described which are found only upon their gills and in the cellular tissue. In an aquarium, whenever an injury happens to any of its inhabitants, the wounded surface is seen at once to be covered with fungoid growths, which often attain a large size. But it is the insect tribe which suffers most from this cause; for their diminutive size is little able to cope with the parasite, which when once fastened increases at their expense, till it exceeds them in size and destroys them. Flies may be seen at certain seasons struggling through the air with long stems attached, the mycelium of which spreading inward stops their breathing tubes.
Certain species of sphoerioe grow within the larvae of insects in China and Australia, and completely mummify them, so that they resemble twigs of wood, from which sprout forth branches. The most important of all, in an economic point of view, is the botrytis Bassiana, which is so destructive to the silkworm. This disease is called muscardine. The spores enter the air tubes of this worm, sending their mycelium through its tissues, and always cause its death. After this the plant pushes its fruit-bearing stems into the outer world, and converts its victim into a mass of mould, from which fresh spores are sent off to spread the disease. Although it only attacks the larvae, it may by inoculation be cultivated upon the chrysalis and moth. The intestines of insects and worms which live in decayed wood are often found filled with most curious forms of vegetative life, as Dr. Leidy has shown in the case of the iulus terrestris, and the very entozoa which dwell within their intestines are covered with similar growths. - Those who would pursue this subject still further will find much to interest them in the following works: Robin, Histoire naturelle des vegetaux parasites (2 vols. 8vo, Paris, 1853); Kuchenmeister, "Manual of Parasites," translated for the Sydenham society (2 vols. 8vo, London, 1857); Berkeley, " Introduction to Cryptogamic Botany;" and Leidy, "Flora and Fauna within Living Animals," in the " Smithsonian Contributions to Knowledge," vols. v. and vi. (Washington, 1853 and 1854). - The term epiphytes is also applied by botanists to plants which grow upon other vegetables, but which do not derive their nourishment from them. (See Air Plants.)