56 A TEXT-BOOK OF BOTANY. 



Single trees are treated by removing the affected branches and 

 painting over the cut ends with coal tar to prevent reinfection. 



For further details on this fungus consult : Murrill, " A New 

 Chestnut Disease," Torreya, Sept., 1906; Farmers' Bulletin 467, 

 U. S. Department of Agriculture ; Metcalf, " Diseases of the 

 Chestnut and Other Trees," Trans. Mass. Hort. Soc., August, 



FIG. 32. Chestnut-blight disease, which occurs in small yellowish pustules the size 

 of a pin head. A, section of pustule showing perithecia; B, asci with sporidia; a, usual 

 form; b, form rarely found; C, sporidia; D, summer spores. After Murrill. 



1912 ; Farlow, " Fungus of the Chestnut-Tree Blight," Science, 

 May 10, 1912. 



BASIDIOMYCETES. The Basidiomycetes are the most highly 

 organized of the Fungi. The mycelium consists of white branch- 

 ing threads and is usually concealed in the substratum. In the 

 cultivation of the edible mushrooms propagation is by means of 

 the mycelium, which is known commercially as " spawn." It is 

 recognized, however, that mushrooms can not be propagated in 



