60 



It is evident then that the underground stages of fungi both because 

 of their long-continued presence in the substratum and universal occur- 

 rence must be of more consequence to the rest of the plant world than the 

 rather rare and short-lived spore-bearing part. From such considerations. 

 a very natural line of inquiry leads one to consider the food habits of the 

 fungus threads and it is here that the usefulness of the family in nature 

 becomes apparent. 



As every one knows, a great deal of all vegetable matter is carbon, a 

 fact w^hich needs only the ra.ention of charcoal to be quite evident. 

 This carbon can be obtained in quantitv from only one source — the air. 

 The carbon dioxide of the air is absorbed by the green plants and manu- 

 factured into its tissues, wood, bark leaves, etc. It is easily demonstrat- 

 ed that about half the dry \veight of a tree is pure carbon all of which 

 must have come originally from the air. The amount of carbon that is 

 thus "bottled up" in all the forests, fields and prairies of the world is 

 simply enormous, and \vhen each season's gro\\'th is considered as add- 

 ing to the amount it makes one rather uneasy as to whether the supply 

 of this indispensable material will hold out for any length of time. 



When we turn to the only source of supply of this important sub- 

 stance — the air — it is astonishing to find that it contains but a mere 

 trace of carbon dioxide: about a third of one per cent in fact. It is so 

 scarce that the carbon necessarv for a single ordinary tree would exhaust 

 the supply from the air fiftv feet deep over a hundred acre farm. Now if 

 one thinks of the vast number of forest, fruit and shade trees of the land 

 to say nothing of the grain, grass and vegetables, all of which must have 

 a share, we begin to loo-< forward hopelessly to a carbon famine, a very 

 imminent time of distress when all the green things will cease to grow 

 for lack of this indispensable m.aterial. 



That such a terrible possibilitv has never been realized is almost en- 

 tirely due to the much despised toadstool and his numerous fungus rela- 

 tions. Unable themselves to utilize the carljon of the air because they 

 lack the necessarv green coloring matter, they are content to use that 

 which they find in the dead stems, leaves, etc. of other plants. By means 

 of powerful ferments thev break' up the tissues of these and after using 

 the carbon give it back to the air again as carbon dioxide. So constantly 

 and universallv is this process carried on that the supply of carbon diox- 

 ide in the air is renewed as fast as it is removed by the green plants. 

 Thus there is a continual circulation of carbon in nature, from the air to 

 green plants, from these to the funsfi which live in them after their death 

 and then back to the air again. It must be evident that ^vithout the 

 presence and co-operation of these humble organisms the limited stock of 

 carbon dioxide in the air would in a very few vears be so entirely ab- 

 sorbed and locked up in the vegetable matter of our forests and fields 

 that no further growth could take place. All vegetation would perish 

 and with it all animal life including man himself. 



Such is the role of the lowly toadstool and his allies, and one can 

 hardly help feeling a considerable respect for them as they persistently 

 and unobtrusivelv perform their verv necessarv part in the harmonious 

 working out of Nature's great plan. 



