FUNGI 529 we learn that a single plant produces millions of these reproductive bodies, so small that they float on the air scarcely influenced by the force of gravity, that they may remain an in- definite period inert, and be called into sudden vitality by atmospheric changes favorable to their germination, their sudden appearance can be readily understood. They have been traced through their metamorphoses. The infinitesi- mally small spore has been watched in its growth into a perfect plant ; and one such observation, unquestionably made, is positive proof of their being perfect plants, having a development following certain laws. Fungi are of purely cellular growth. They form no woody fibre like flowering plants, though many become corky, woody, and horny in the course of their growth, nor do they form chlorophyl in their tissues. They consist of mere aggregations of homogeneous cells, but exhibit a wonderful va- riety of external forms. Their earliest vegeta- tion is a prolongation of the membranes of their spores, a name given to their reproductive sem- inal dust, which, though performing the office of seeds, differs from true seeds in being mere individual cells. From these arises a delicate, minute, webby growth, called the mycelium, which is the true vegetation of the plant, and which gives rise to the reproductive bodies at once, or builds up a receptacle which contains them. It is this mycelium which penetrates and destroys the object on which it is parasitic. It is made up of radiating and intertwining fibres formed of rows of cells placed end to end. These are in many instances so minute that they easily traverse the tissues of living plants and the pores of solid wood. From this my- celium grow the spores, which in their simplest form consist of the terminal cell or cells, which drop off to form new plants. They are of the extremest minuteness, appearing to the eye like a mere cloud of impalpable powder. As we rise in the scale, special branches and processes are formed to bear the spores, either singly or in groups. Still more complex forms build up a special organ called the peridium, within which the spores arise contained in little sacs termed asci. The large fleshy growths met with in the woods or on trees are processes belonging properly to the reproduction and not the vegetation of the plant. They are very dis- proportionately large compared with the my- celium, and consist of a main stem called a stipe and an expanded top called a pileus, on which these spores are borne in various ways, on gills, ribs, prickles, &c. The mycelium is sometimes reduced to a mere trace of eva- nescent, floccose growth ; while the reproduc- tive body becomes a fleshy mass, several pounds in weight. But the spores are always minute, being sometimes only -^5,^5 of an i nc ^ in diameter. Fungi occupy an intermediate position between algas and lichens, into which orders they gradually merge at different points. Indeed, so nice is the distinction at times, that some systematists have reduced lichens to a suborder of fungi. They differ from lichens mainly in deriving their sustenance from the object on which they grow (though this has exceptions), in not producing a foliaceous thal- lus, and in not forming green chlorophyl ; from algaa, in being aerial, not aquatic, and in deri- ving their nourishment from their matrix and not from the surrounding medium. Those species of fungi which are found in fluids, such as the yeast and vinegar plants, are now proved to be merely submerged mycelia of certain moulds (penicillium), which do not attain their perfect stage until they reach the air. Their propagation in fluids is due to a power the my- celium possesses of retaining its vitality under a variety of circumstances, of suffering divi- sion and enduring extremes of temperature. Besides this, it has a propagating power anal- ogous to that of budding. In some aerial forms it goes on reproducing itself in peculiar ways, and rarely reaching the normal or perfect as- cigerous fructification. For this reason many species have been thought to be distinct plants when they are merely arrested stages of growth of one single species. Some aerial forms nev- er reach a further growth than a compact, dense mass of mycelium. Oak trees sometimes contain a solid mass of a leathery texture (xylostroma giganteum), which never advances beyond that stage. The genera sclerotium and rhizomorpha, with their so-called species, are mere compact bodies of mycelium, which have in some instances been artificially forced to develop themselves, and have produced plants of widely different structure. The ergots of grain are the ovary arrested in its proper development and transformed into a peculiar growth by the presence in its tissues of a mi- nute fungus. Tulasne and others have watched their development into species of cordyceps. These forms remain constantly arrested; but very many of those which under favorable circumstances reach perfection remain similarly checked, and confuse the student with their multiple forms. This has caused the naming of hosts of species which are merely forms of others. There is no branch of science whose synonymy is more burdensome. It is almost a hopeless task to attempt to identify the spe- cies of authors by description alone, the plant itself being necessary for comparison. Long and continued observations are required to de- termine and connect the many forms which a single fungus may assume in the course of its existence. Few objects in nature exhibit more gorgeous colors. The larger fleshy forms pre- sent an endless variety of graduated tints. Some of the loleti exhibit on being broken a remarkable change of color, the white or yel- lowish hue of the interior changing instantly to a vivid blue. This is supposed by Frof. Robinson to be due to a molecular and not to a chemical change. Their texture is as varia- ble as their color. Some are almost fluid, ot ers fleshy, papery, leathery, corky, or har and horny. Their size is equally various, from
