The rank of this plant in the vegetal kingdom is settled by the direction of growth of its vegetative system and by the nature of its tissues. All flowering plants, as well as the ferns and mosses, have their vegetative part made up of root, stem, and leaves. The root grows downward and the stem upward. But the growth of the mycelium, the vegetative system of the mushroom, is horizontal; there are no signs of such organs as root and stem. In this respect it is on a level with lichens and sea-weeds, and belongs at the foot of the scale in vegetation. As respects the nature of its tissues and the absence of woody fibre in its composition, it resembles all the flowerless plants except ferns. But where are its immediate kindred? Have mushrooms no nearer relations than mosses, lichens, and sea-weeds?
To answer this question intelligently we must further observe the structure of fleshy fungi. In the common mushroom, as we have seen, the hymenium is spread out upon the lamellated structure of the gills—an arrangement, however, which is not general. It is peculiar to a single group known as agarics. This group has also the further general characteristic of preferring to grow in shady places. But in this latter respect the common mushroom is an exception. In its wild state it flourishes best in meadows and pastures. Its scientific name is composed of two words: one tells us the immediate group of toadstools to which it belongs, and the other expresses this exceptional feature in its constitution. The one which is put first is its family or surname, Agaricus; and the specific name, or what we may call the "given" name, is campestris (meaning field). These names are written in Latin for the convenience of the botanists of different nations speaking different tongues, but for whom the Latin is a common medium of communication.
Now, the structure of the under portion of the cap in some toad-stools is porous instead of lamellar. The surface of the spore-bearing hymenium is multiplied by means of pores or tubes which penetrate the substance of the cap, as seen in Fig. 4. Two stemless species of this sort are shown in the plate as growing upon an old tree.
Sometimes this under surface is seen to be quite smooth, or it