Somehow or other, through sympathy perhaps, we are more willing to pardon saprophytism than parasitism pure and simple, and Nature apparently takes the same view of the case, for the saprophytes include all the largest and finest specimens of the fungus kind. Mushrooms, toadstools, earth-stars, puff-balls, stink-horns, truffles, bracket-fungi, are nearly without exception saprophytes. Such fungi, too, as we see, have won attention and enjoy something of a popular classification. This classification science largely confirms—not wholly; and it is interesting to notice that it is just where the popular classification is weak that science fails to discover difference. Many a country wight and many an epicure as well would deem it rare fortune could he learn to distinguish invariably toadstools from mushrooms. Suppose we say that toadstools are poisonous while mushrooms are not. A toadstool, accordingly, is a poisonous mushroom, and a mushroom is an edible toadstool. The only possible means, therefore, by which the two may be distinguished is a test direct, as in the old rule which bids the inquirer eat with the assurance that, if he survive, he has eaten a mushroom; if he die, a toadstool. But some species»poisonous to one person are by no means so to another; so that even the rule just quoted is unsatisfactory on the score of being inconclusive, as well as inconvenient of application. Even Agaricus muscarius, esteemed so very poisonous to ordinary mortals, is said to produce in the Kamtchatkan simply an increase of that pleasing stupidity which the Chinaman seeks in his opium-bowl or the American in 
Fig. 1.—Fruit of Green Mold (Penicillium glaucum). his beer. Furthermore, Science runs her lines not as between toadstools and mushrooms, but as between specific forms. Poisonous and not poisonous, edible and inedible, are side by side in any enumeration of species. Let it be once known which are edible species, and these may thereafter be readily recognized by any one competent to discern a species—no easy matter, by the way, even to the practiced student.
So much for popular estimate and classification. Let us now briefly consider fungi from the standpoint of structure, the true basis of classification or distinction. A bit of mold placed on the stage of our microscope will enable us to make a beginning (Fig. 1). Here we have cells, of course, tubular in shape and disposed to form thread-like branches in different directions. These threads are known as hyphæ, and fungi generally are masses of
