100 APPLIED BIOLOGY 



food if we first study the nutrition of plants like the mush- 

 rooms and the Indian pipe (Monotropa), which have no 

 chlorophyll. Such plants get their food-materials entirely 

 from the soil in the form of (1) certain inorganr& or mineral 

 substances which are commonly found dissolved in water 

 in good soils, and (2) organic materials absorbed from the 

 decomposing matter, such as the leaf-mold, on which mush- 

 rooms and the Indian pipe commonly grow. 



The water obtained from the soil by mushrooms contains 

 compounds with the elements nitrogen, and also in various 

 combinations are other elements (e.g., calcium, phosphorus, 

 sulphur, potassium, magnesium, iron) which chemists find in 

 analyzing such plants. These necessary elements may come 

 in part from the decaying organic materials in the soil. 



It is from this decaying matter only that the mushroom 

 can get the indispensable foods known as carbohydrates, a 

 term which means a compound containing carbon (C) and 

 water (H 2 0), and therefore composed of the necessary ele- 

 ments carbon, hydrogen, and oxygen (C, H, O). Examples 

 of carbohydrates are starch, sugar, and cellulose (the chief 

 substance in plant cell-walls). 



Now, mushrooms and other plants without chlorophyll 

 cannot make such foods as starch and sugar, and so they 

 must use these foods made by some pre-existing plant which 

 had chlorophyll ; that is, they must live on leaf-mold or 

 other decaying plant matter from which they can absorb 

 carbohydrate food in a dissolved form, usually as sugar. 

 These foods which are absorbed by the cells of the mush- 

 room are used by its protoplasm in the life-activities of the 

 cells, especially in making new cell-materials into which the 

 nitrogen and the other necessary elements named above are 

 also combined. 



Saprophytes and Parasites. Plants which get their 

 carbohydrate foods from decaying organic matter are often 

 called saprophytes (from Greek words for rotten and plant). 



