Molds
low forms of flowerless plants. Molds are related to microscopic bacteria and yeasts, but are easily seen. They grow in masses, consisting of innumerable threads. An examination of mold growing on a decaying strawberry, plum, peach, potato, lemon, a piece of bread, bit of leather, slimy wall, rotting chip, old cheese, neglected ham bone, or exposed preserves, will reveal a mass of slender, thread-like runners following the surface, climbing above and among their fellows, or penetrating deep into the substance on which they feed. Molds have no roots in the ordinary sense of the word. The threads are jointed; that is to say, they consist of slender cells, end to end. Each cell absorbs largely for itself, and when it has had abundance, possibly in a few minutes, sends on a sprout or new cell, which in turn does likewise. Mold starts always on the surface and spreads rapidly.
At first mold plants are transparent and colorless, but in two or three days the fluffy masses grow more dense and felt-like from the crowding of branches, and begin to bear spores. They acquire color according to the kind of mold--creamy, yellow, green, red, blue, and black. A change of color indicates that spore bearing has begun. Botanists recognize molds and name them according to their color and manner of fruiting. Two typical forms of spore bearing may be described. In the case of blue mold, many tiny threads spring up vertically like a forest; each divides into a cluster of branches fine as a spider's thread. The slender branches dry into lines of almost microscopic spheres or spores, like beads on a string. They have a bluish tinge which gives the mold its blue appearance. The spores of black bread mold are inclosed in knobs or pin-head sacs at the ends of the slender branches of the upright stems. When ripe--black--the sac bursts open and sets the spores free.
Spores are exceedingly light. Every breath of passing air carries them away to travel and float and bound about by millions. Most of the spores come to nothing; but whenever one settles on a suitable, moist, lifeless plant or vegetable surface, it adheres, extends slender threads, and grows like its parent with marvelous rapidity. Except in the middle of oceans and deserts, the air is full of mold spores. They are bounding and rolling along over all exposed surfaces. Wherever air goes they go. Wherever one finds opportunity--moisture, warmth, dim light, food--it settles in; sends out a slender thread, and repeats the history of its parent. As food cannot mold without spores, the way to preserve food from molds is to keep the spores out, or else to establish such conditions of heat, cold, or dryness that molds cannot grow. A piece of paper tied over the top of a glass or jar may not keep out bacteria, but it is a sufficient protection against molds, provided spores within have been killed by heat. Exposure to bright sunlight kills any molds or mildew likely to grow on harness or clothing. Molds require moisture; so jellies and fruits keep better in a dry place. A pantry should be dry and well lighted. If canned or pickled goods mold when tightly sealed, the housekeeper may depend upon it that tiny spores were present before the articles were protected. Woodwork, wall paper, curtains, clothing, bedding, shoes, rags, waste paper, and carpets are all subject to molds, or mildews, which are simply molds of small growth. The musty smell noticeable in cellars and closed rooms is due usually to mold, and indicates that a good airing is needed.
Ripe fruit on the tree is covered with a delicate membrane or outer skin that prevents spores from getting a foothold. If the slightest bruise or puncture allows the first mold thread to enter, the mischief is done. For this reason, hand-picked and unbruised fruit is less liable to rot and brings a higher price than windfalls or fruits that show bruises. Fruit that is desired to keep should be handled with care and not thrown or dumped roughly. As long as the skin of an apple or pear is unbroken, mold cannot enter. Bruises that do not show at first make future decay possible and, under ordinary conditions, inevitable.
Strawberries, raspberries, and other soft, juicy fruit cannot be kept fresh for a long time, but an apple is well protected by nature and should keep for months. Shippers wrap fruit in squares of tissue paper for the double purpose of keeping spores out and of absorbing moisture, thus preventing the spores already in the fruit from growing. Molds do not prosper in cold, dry air. For this reason, refrigerator cars packed with ice have been built to carry fruits across the continent. California fruits protected by ice are delivered delightfully fresh in all the cities of North America, and the fruits of the South are likewise sent by the trainload in all directions to the large markets.
Some foods are thought to be improved by mold. Roquefort cheese, for instance, owes its flavor to the particular green mold that feeds upon it. Molds perform a service in beginning the work of breaking up animal and vegetable matter for plant food. They open the way for bacteria. Without molds and other low forms of plants, the higher plants and animals could not long obtain food, and the earth would be uninhabitable. See Bacteria For an account of fungi that attack living plants, see RUST. Ringworm, with one or two other afflictions characterized by an inflammation which proceeds from a central spot and continues its progress in the rim of a circle after the original center has healed, is due to a peculiar mold parasitic on man.