228 
GARDENS AND THEIR MEANING 
XL Study of Bacteria 
Materials. Three test tubes, cotton, boiled potato, fruit or apple 
sauce, three apples, one partly decayed. 
Directions, ia) Fill each tube about one third full of apple sauce. 
Plug each with cotton. Set one aside. Put the other two into a 
pail of water and boil for half an hour. After boiling, set one tube 
aside with the cotton undisturbed. Take the cotton from the third 
tube and leave it out for half an hour or more, then put it in again. 
Leave these for a few days, note what happens and account for 
different results. In canning fruit, is it desirable to leave the fruit 
uncovered for a few' minutes after cooking ? Why ? 
ip) Prick one of the sound apples in several places with a pin. 
Put the pin into the rotten apple and then into the other sound 
apple. Repeat this in several places. Set the two sound apples 
aside for about a week. Note what happens and account for the 
different results. 
NOTES ON SOILS 
I. Soil Materials 
Gravel. Coarse rock fragments. 
Sand. Corresponding in size to grains of sugar. 
Silt. Fine soil particles, smooth texture (for example, silicon for 
cleaning knives). 
Clay. The finest rock particles. 
Humus. Decaying vegetable and animal substances (for ex- 
ample, decaying leaves and twigs). 
II. Soil Variations 
Sa?idy soil. A mixture of sand and small amounts of silt, clay, 
and humus, usually poor in nitrogen. 
Loam soil. A mixture of one half sand with clay and humus. 
Fine, sticky. Good for general farming. The more hurnus the 
richer in nitrogen. 
