With regard to their pilfering habits, such plants are usually proportioned off into two great groups. They either attach themselves to other beings and absorb their juices, in which case they form a mighty host of plants of prey usually known as _parasites_; or they seek their nurtriment, and find it, in dead and decaying organisms, and are then known as _saprophytes_, a somewhat hard word to begin with, for which I can not find a popular equivalent, but which merely signifies plants that grow on decomposing matter. All land plants that are not blessed with a true green color belong to one or other of these groups, and are villains in their various degrees. They make no effort to free the air from the gaseous impurity that haunts it, but, like animals, they keep fouling it instead. With a very few exceptions, all of them subsist on organic matter in some form, and this they usually draw from the plants, living or dead, on which they grow, or from decaying matter in the soil. But many of these vegetable villains run into half-honest vagaries, and succeed in raising themselves slightly above the common ruck. If they can not seize and break up carbonic acid gas, they may do a little toward atmospheric purification of a kind by laying fast hold on such organic particles as are floating in the air or brought to them in falling moisture. Plants such as these are sometimes found growing on barren sand, on hard gravel, on parapets of bridges, on leaden cisterns, on plastered walls, on slag, and in like inhospitable places, where they are compelled to turn mainly to the atmosphere and trickling moisture for food. Some such haunt mines like phosphorescent ghosts, others make themselves at home on places like the dome of St. Paul’s Cathedral. In a mass two feet in length, similar strange plants were one morning long ago found by a smith on a piece of iron that he had taken, on the previous night, red-hot from his fire, and laid on his water trough. Many similar vagaries they run into that would in the telling sound almost incredible. Indeed, the whole group of the saprophytes is not to be accounted so utterly abandoned as that of the parasites. To these they are certainly nearly related, but there is more of the useful scavenger about them than of the useless thief. No sooner has death overtaken any plant than a host of them set to work to clear away the now useless organism from the world, breaking down herbaceousness into putrescence, timber into touchwood, and all at last into vegetable mould. Their mission is to seize upon decaying matter and endow it with life in a new form; and thus out of rottenness often comes wholesomeness, decay moulding itself into pleasant mushrooms, or into things unfit for human food perhaps, but that may bring the blessings of abundance to many little living creatures. If such as are edible are to be considered villains, then people of delicate palate who smack their lips over some of them have a