Natural History 009 



more favourable. On the thrift of the plant in this respect the 

 human race depends. 



Finally, the carbohydrates, in the leaf or after transport 

 elsewhere, are used to form other substances, such as cellulose, oil, 

 chlorophyll, and living matter. In intricate ways the salts from 

 the soil help in the transformations. 



2 



Nutrition of the Fungi 



There are, however, some plants which possess no chloro- 

 phyll, and are in consequence unable to build up for themselves 

 organic food from inorganic materials. Most familiar are the 

 multitudinous fungi, which have probably been evolved from 

 various groups of alga?, and include such diverse types as the skin 

 of blue mould on jam, the fur of black mould on bread, the 

 fawn-coloured mushroom of the meadows, the bright-hued toad- 

 stools of the woods, the rust disease of wheat, the mildew of goose- 

 berries, the blight of potatoes. All these and innumerable others 

 are dependent on the organic food formed by some other plant. 

 One group called saprophytes feeds on decaying organic matter, 

 another group called parasites subsists on living hosts. The toad- 

 stool and the mushroom grow in the soil like any green plant, but 

 in situations where the soil is rich in organic matter; the toadstool 

 lives in the leaf -mould of the wood, the mushroom in the well- 

 dunged pasture. The food-supplies of the fungus mould on bread 

 or jam, or of the mildew on the gooseberry, are obviously gener- 

 ous. From such sources the fungus draws its nourishment ready 

 made. 



Saprophytic fungi may play an important part in aiding bac- 

 teria to break down dead organic matter into inorganic com- 

 pounds, which may be used once more by green plants. Some 

 are of direct economic importance on account of the by-products 

 of their vital processes; thus the yeast plant is a fungus which 

 forms alcohol from sugar. 



