266 APPLIED BIOLOGY 



Ants raising Mushrooms. One of the interesting members 

 of the mushroom group is a species which is regularly culti- 

 vated by the leaf -cutting ants of the tropics. Pieces of leaves 

 are chewed by the ants and then packed away to decay and 

 form a proper substratum for the growth of a mycelium, 

 which is eaten by the ants. 



Physiology of Mushroom. As described in 98, plants with- 

 out chlorophyll are like animals in that they must get their 

 food from other plants, either as parasites on living plants 

 (e.g., dodder), or as saprophytes on decaying plant matter. 

 The common mushrooms are usually saprophytes, but some 

 of them grow as parasites on living trees (e.g., shelf-fungi). 



In their breathing mushrooms are like animals in that 

 they take in oxygen and excrete carbon dioxide. 



248. Lichens. The familiar plants known as lichens, 

 which in the form of grayish scales or moss-like masses 

 grow on rocks and bark of trees, consist of two kinds of plants 

 living together in intimate connection. One of the plants 

 is a member of the Algae ( 236), and able to make carbohy- 

 drates from carbon dioxide and water; while the other is 

 a fungus, which obtains its carbohydrate food from its 

 associate. The main mass of a lichen is a dense mycelium 

 similar in microscopic structure to some mushrooms, and 

 in this are the cells or filaments of the associated green plant. 



Such a living together is an example of symbiosis. A 

 similar association between a plant and an animal is described 

 in 285. 



It is possible to collect the spores and grow separately 

 the two kinds of plants included in a lichen. 



Reindeer-moss (a valuable food for reindeer) and Ice- 

 land moss (used in cooking) are lichens. Litmus (used for 

 testing acids and alkalies) comes from a lichen. On the 

 mountains lichens assist in weathering rocks, and thus form- 

 ing soil. An edible form found on sandy deserts is called 

 manna-lichen. 



