440 NATURE STUDY AND LIFE 



bacteria with them, 43,830 different kinds are now described, 

 nearly one-quarter of all the plant species known to science. 

 In size they range from large mushrooms and giant puff- 

 balls, of many pounds in weight, to moulds and bacteria, 

 so small that it would require 10,000 placed side by side to 

 measure an inch, — far too minute to see with the unaided 

 eye, even as a speck of dust on a polished mirror. The 

 prime characteristic of this large group is absence of the 

 green coloring matter, chlorophyll, of the higher plants. 

 Lacking this, the fungi are unable to build up living matter 

 from the elements by the aid of sunlight; hence, they 

 commonly grow in dark or shady places, and they must 

 depend for their food upon other organisms, animals, or 

 plants, either dead or alive. While we shall find many 

 and beautiful colors, the prevailing tone throughout the 

 whole group is white or gray. A few of the higher 

 plants, notably Indian pip;, pine sap, dodder, have lost 

 more or less of their chlorophyll and, at the same time, 

 have become parasitic upon other plants. Those fungi 

 that live upon dead matter are saprophytes ; those that live 

 upon the tissues of plants or animals to their detriment are 

 parasites. Still other species, especially bacteria, subsist 

 upon or in living organisms with mutual benefit and are 

 called symbiotes, i.e., "together-livers." 



When we inquire what this group of plants does in the 

 economy of nature, we must study them in connection with 

 their foods, as above specified. 



By far the greater number subsist upon dead matter — 

 the remains of animals and plants. Imagine all the trees, 

 plants, and animals that have died since the world beo-an, 

 whose bodies did not happen to have been burned or eaten, 



