336 PLANTS WITHOUT CHLOROPHYLL 



Fungi of our Homes. — But not all fungi are found in the open. 

 Some have become introduced into our homes and live on some of 

 our food or on other materials. These plants are very important 

 because of their relation to life in a town or crowded city. An 

 example of such a plant is the bread mold (page 222). 



Physiology of the Growth of Mold. — Molds, in order to grow 

 rapidly, need food, darkness, oxygen, moisture, and moderate heat. 

 They obtain their food from the materials on which they live. 

 This they are able to do because the rhizoids give out digestive 

 enzymes which change the starch of the bread to sugar and the 

 protein to a soluble form which can be absorbed by the cells. 

 These absorbed foods are then used to supply energy and make 

 protoplasm. Thus molds act like animals, except that digestion 

 takes place outside of the body. 



What can Molds live on? — We have seen that black mold lives 

 on bread. We find also that it and some other molds (e.g. green or 

 blue mold) live upon decaying or overripe fruit. Molds feed upon 

 all cakes and breads, upon meat, cheese, and many raw vegetables. 

 They are almost sure to grow upon flour if it is allowed to get damp. 

 Jelly and other foods containing moisture are particularly favorable 

 to molds. Shoes, leather, cloth, paper, or even moist wood will 

 give food enough to support their growth. At least one trouble- 

 some disease, ringworm, is due to the growth of molds in the skin. 



What Mold does to Foods. — Mold usually changes the taste 

 of the material it grows upon, rendering it ^' musty ^^ and some- 

 times unfit to eat. Eventually food will be spoiled completely 

 because bacterial decay sets in. Some molds are useful. They 

 give the flavor to Roquefort, Gorgonzola, Camembert, and Brie 

 cheeses. But on the whole, molds are pests which the housekeeper 

 wishes to get rid of. 



How to prevent Molds. — As we have seen, moisture is favor- 

 able for the growth of mold ; conversely, dryness is unfavorable. 

 Inasmuch as the spores of mold abound in the air, materials which 

 cannot be kept dry should be covered . Jelly, after it is made, should 

 at once be tightly covered with a thin layer of parafiin or waxed 

 paper, which excludes the air and possible mold spores. To pre- 

 vent molds from attacking fresh fruit, the surface of the fruit 

 should be kept dry and, if possible, each piece of fruit should be 



