Minnesota Plant Diseases. 



271 





ting or by the decay of the walls. These capsules are not con- 

 spicuous and are not met with frequently. For a more com- 

 plete account of the life history of these fungi the reader is 

 referred to Chapter IX. The growth of this mold is favored by 

 close, moist conditions. 



Slime flux of trees. Slimy, mucilaginous material can some- 

 times be found flowing from wounds in oak, apple, birch, elm, 

 maple and other trees. The wound in itself may not be due 

 to any fungus disease but may be caused by pruning, frost or 

 sunscald, etc. In the slime which proceeds from the wound, 

 however, one usually finds a simple form of the sac fungi (an 

 Endomyces) closely related to the mold of the honey mush- 

 room, and to the yeast fungi. The fungus mycelium is com- 

 posed of branched threads, on which the simple four-spored 

 sacs are found. There is considerable doubt that the Endo- 

 myces is the cause of the slime flux. In the flux one may also 

 find one or more yeasts and other fungi, bacteria and plants be- 

 longing to the blue-green algae. Through the agency of the 

 yeasts fermentation often sets in and the flux may then have 

 an odor of beer. Slime-flux wounds often increase in size until 

 large areas of bark die off and the whole tree may subsequently 

 die. Shade and park trees are sometimes killed off in this 

 manner. As the cause of the flux is not definitely known, 

 methods of prevention are not understood. The usual precau- 

 tions which are recommended for treatment when trees are 

 pruned should be followed. 



Witches'-broom of birch (Species of Exoascus). Cultivated 

 birches are sometimes attacked by this fungus. The results are 

 seen in the production of witches'-brooms, somewhat similar to 

 those produced in cherries. The fungus is a similar one and 

 produces its sacs on the twigs and leaves. The infected por- 

 tions should be cut back and burned. 



The Nectria of red-knot TQi\Ncctria cinnabarina (Tode) Fr.]. 

 This fungus is not uncommon in the state. It is a wound par- 

 asite, gaining entrance to the inner bark of the tree by such 

 wounds as are produced by hail, birds, squirrels, storms or 

 pruning. Infection takes place from the mycelium which 

 grows into the bark from the wound and establishes itself in 

 the water-conducting tissues of the wood. By continued 



