THE TREE ITS ROOT-SYSTEM. 97 



tubes of a cellulose-like substance, filled with the living 

 protoplasms of the fungus, and possess the remarkable 

 property of being able to bore their way through or be- 

 tween the cellulose walls of the roots. The fungus at- 

 tacks the plant about the second year, and it is not dif- 

 ficult to find true root-hairs on the young root-system 

 when the apices are still free from the fungus mycelium. 

 The parts of the root attacked alter their form slightly ; 

 they grow more slowly in length, and assume a fleshy, 

 coral-like appearance (Fig. 7, m). Such a fungus- 

 clothed root is called a mycorhiza, and the view is gain- 

 ing ground that the symbiosis between the fungus and 

 the root is of advantage to the oak. It has even been 

 suggested that the mycelium performs the functions of 

 root-hairs to the root, absorbing water and nutritive 

 materials from the soil and passing them on to the oak, 

 in return for a certain small proportion of organic sub- 

 stance which the latter can well afford. At any rate, it 

 may be that the fungus hurries the decomposition of 

 vegetable remains in such a way that they become avail- 

 able to the root sooner than would otherwise be the case. 

 The systematic position of these remarkable fungi is not 

 yet ascertained, but there is some evidence for the view 

 that the mycelium is that of a truffle, though the ques- 

 tion is still an open one. 



