Algae, Fungi, and Lichens. 



283 



part that has accumulated the food necessary to main- 

 tain the very rapid growth which toadstools are so 

 well known to make. The student will notice by a 

 careful examination of the sub- 

 stratum that it is very rich in 

 vegetable remains in the form of 

 mouldering leaves, stems, roots, 

 etc., whose substance the toad- 

 stool is able to digest by means 

 of ferments excreted from its un- 

 derground filaments. 



But the toadstools and their allies 

 do not always restrict themselves 

 to this innocent mode of life, for it 

 may happen that underground fila- 

 ments, ramifying through the rich 

 mould of a forest in quest of food, 

 penetrate the roots of a tree, and 

 entering the woody tissues, digest 

 and appropriate them for food 

 (Fig. 146). So the Fungus advances 

 deeper into the roots, and up into 

 the stem, sapping their strength, 

 until the tree may easily be broken 



off or upturned by the wind. These Fungi also gain 

 access to the interior of the trees through wounds in 

 the bark, or through the broken branches of the above- 

 ground parts. (Figure 147 shows a portion of a trunk 

 of a tree which has suffered from the ravages of Fungi.) 

 In some localities forest trees suffer considerable dam- 

 age from foes of this kind; and not only trees, but 

 timbers also which have already been put to purposes of 

 construction. 



Fig. 146. 



Destruction by Fungi of a cell 

 of pine wood. The branched 

 filament is a paii of the my- 

 celium of the Fungus. The 

 upper part of the wood cell 

 has not yet been disinte- 

 grated by the Fungus, as has 

 the lower doited part. After 

 R. Hartig. 



