DISEASE CAUSED BY FUNGI 207 



of spruce are often attacked by a fungus called Peridermium 

 coruscans; as a result the leaves become shorter and suc- 

 culent, and in this condition have been used as food. 



As would be expected when such distortion takes place, 

 the microscopic structure is much disturbed, certain systems 



. w r 

 n 



FIG. 54. Exobasidium rhododendri, a primitive type 

 of a basidiomycete parasitic on leaves of Rhododendron 

 ferr^lg^ne^lm, where it forms large galls, i, branch of 

 Rhododendron, with galls on the leaves formed by the 

 fungus ; 2, basidia of the fungus bearing a variable 

 number of spores. Fig. i, reduced ; fig. 2, highly mag. 



of tissue are developed in excess, whereas others are equally 

 arrested. A detailed account of such changes is given by 

 Kiister. 



Although saprophytic fungi do not injure living plants, 

 nevertheless many such are of economic importance, and 

 rank amongst the most destructive of fungi. 'Dry rot' 

 caused by Merulius lacrymans, a true saprophyte, is an 



