Experiment 112. -(1) Bruise a sound apple and place the bruised part in contact with a thoroughly rotten apple. Wrap the two up together in a wet cloth and put in a fruit jar. Seal the jar to prevent the water from evaporating.
(2) Plunge a pin repeatedly first into a rotten apple and then into a sound one.
Wrap the sound apple in a wet cloth and seal in a fruit jar. (3) Place a lemon which has developed a green, spongy, rotten place in it in contact with a perfect lemon and keep them where they will be moist. What happens to the sound fruits?
The plants that we have so far studied are green plants and contain chlorophyll. They are able to prepare their food from the air and soil by the aid of the sun"s energy. There is, however, another great group of plants which have no chlorophyll and which are obliged to live upon the food that green plants have prepared. They find this food either in the living or in the dead parts of plants or animals, the animals having digested it from plants or other animals who originally obtained it from plants.
Plants that have no chlorophyll and live upon the food green plants have prepared are called fungi. The bacteria belong to this group. If plants live upon living plants or animals, they are called parasites, if upon dead ones, saprophytes. Plants of this kind are exceedingly important, although many of them can be seen only with the microscope.
Without them the earth would soon become uninhabitable. Some of them are injurious to plants and animals, but a large number are most beneficial.
These plants cause the decay of dead animal and vegetable matter. If it were not for them, all the plants and animals that die upon the earth would encumber its surface indefinitely with their bodies, and none of the material that they have taken from the soil would return to fertilize it.
MISTLETOE GROWING ON AN OAK.
An interesting parasitic plant.
These plants make possible the manufacture of vinegar, some cheeses and a great many other things which we use daily.
On the other hand, the decay in fruit, the mold on bread, the corn smut, the smut on oats and barley, the potato blight, the scabs of apples and potatoes, the rusts on grains and many other common plant diseases are simply fungus plant growths. The wheat rust alone costs the United States many millions of dollars each year. Thousands of feet of timber are destroyed yearly by the wood-destroying fungi. Dry rot of timber, as it is called, is due to a fungus growth. The fight against these harmful fungi costs millions of dollars each year.
But some fungi are exceedingly useful. The fungus most commonly made use of is the yeast plant. In bread making, yeast which contains the little yeast plants is mixed thoroughly into the material which is to compose the bread, and the bread is then put into a warm place to rise or, more exactly, to grow yeast plants. If the materials and the temperature are right, the yeast plants grow very rapidly, feeding upon the material of the dough and changing the sugar into carbon dioxide and alcohol. Little bubbles of gas are developed throughout the dough, making it slightly porous.
The bread is then kneaded to mix the greatly increased number of yeast plants still more thoroughly and is allowed "to rise" again. The plants are by this time very uniformly scattered through the dough andthey develop little bubbles of carbon dioxide throughout the mass so that a light sponge results. When this is heated in the oven, the tiny bubbles of gas expand, making a more porous sponge, the alcohol evaporates, and the dough hardens, thus forming light bread. Although the study of these minute fungi is very interesting, it must be done by aid of the microscope and will not be attempted here.
We are most of us familiar with some of the larger fungi such as the mushrooms (Fig. 103) and toadstools. Mushrooms are widely used as a delicacy and their growth is an important industry in some sections. They are grown in soils very rich in humus and generally in dark, cellar-like places. The mushroomsFig. 103.
that grow wild in the woods are abundant in
some localities but should not be used for food unless most carefully examined by some one who is expert in determining the different species. There are several species of mushrooms which are exceedingly poisonous. For one of these there is no known antidote. The general structure of these larger fungi can be seen by examining a mushroom obtained from the market.
Experiment 113. -Place a slice of freshly boiled potato in each of five clean 4-ounce wide-mouth bottles. Close the mouths of the bottles with loose wads of absorbent cotton. Place four of thesebottles in a sterilizer and sterilize for half anhour. Allow one bottle to remain unsterilized. (A sterilizer can be made by taking a covered tin Pail and putting into the bottom of it a bent piece of tin with holes punched in it to act as a shelf on which to put the bottles. A shallow tin dish with holes in it is good for the shelf. There must be holes so that the steam will not get under the shelf and upsetit. Fill the sterilizer with water to the top ofFig. 104.
the shelf and place the bottles on the shelf. Keep the water boiling.) A reliable inexpensive sterilizer is the pressure cooker shown in Figure 104.
