THE CARE OF SHADE TREES— III. 



Fungous Diseases. 



^T is a matter of common observation that 

 fungi play a very important part in the 

 life of many trees, and frequently the 

 ^ most serious disturbances of their vital 

 processes are broug-ht about by the action of 

 these lowly org-anized plants. It must not be 

 suppose, however, that all the fung^i, living- in 

 vital connection with trees, are harmful, for 

 recent studies show that many of our common 



i-^""^ 



Fig. 1770. Agaricus nielleus (Tree Root-Rot). 



A group of plants clustered at the base of a 



tree, and showing the cap, stalk and gills. 



The spores are set free from the edges 



of the gills. (After Massee). 



trees, such as pine, spruce, tamarack, beech, 

 oak, hazel, hornbeam and birch, have their 

 fine rootlets covered with a sheath of fung- 

 ous threads by means of which the feeding- 

 processes are accomplished. These fungous 

 threads, or mycelium, take the place of the 

 root-hairs of ordinary plants, and absorb 

 the food materials from the soil. There are 

 other examples of the fungi and roots living 

 in intimate vital connection, and for their 



mutual welfare. Most of the members of 

 the heath family, most of the perennial plants 

 living in meadows on peaty and humous 

 soils, and the members of the legume family, 

 have fungi living symbiotically with the 

 roots. 



Inasmuch as fungi are incapable of manu- 

 facturing plant-food out of inorganic food- 

 materials, and must feed upon the already 

 prepared food in the decaying vegetable mat- 

 ter of the soil, it becomes highly necessary 

 that the supply of humus be maintained in 

 the form of litter and forest mould in our 

 parks and woods. 



The fungi affecting shade trees may, very 

 conveniently, be divided into three classes, 

 according to the parts of the trees they af- 

 fect : I. P'ungi affecting the roots and base 

 of trunk ; 2. Fungi affecting the stems ; and 

 3. Fungi affecting the leaves. 



I . Fungi affecting the Roots and Base of 

 Trunk. — The entrance of fungi into the 

 roots of trees is determined to a large ex- 

 tent by the conditions of situation and cli- 

 mate. Where the tree has been weakened 

 by any of the physiological causes discussed 

 in the Februar}- number of this magazine, 

 the roots are unable to prevent the develop- 

 ment of those fungi which find an entrance 

 into the tissues. 



(a) Tree Root- Rot. [Agaricus nw/leus). — 

 This destructive toad-stool is a very common 

 fungus, not only on all kinds of fruit trees, 

 but also on the forest trees, shade trees and 

 conifers. The cap of the toad-stool, when 

 full grown, is two inches across, and has a 

 honey color. The stalk is often four inches 

 high, and the gills and spores are white. 

 (Fig. 1770.) 



The spores are distributed by the wind 

 chiefly. On germination delicate, cob-web- 

 like threads are produced, which soon form 

 a blackish covering on the roots. The roots 



