414 



THE FUNGI WHICH CAUSE PLANT DISEASE 



Spores hyaline 10. Hydnum, p. 414. 



Spores colored 11. Phaeodon. 



Teeth iammeliform 12. Sistotrema. 



Teeth connected at base, coriaceous 



Cystidia none 13. Irpex, p. 415. 



Cystidia present 14. Hydnochsete. 



Sporophore perennial, punky or woody 



Upper surface smooth, or sulcata 15. Echinodontiuin, p.415. 



Upper surface zonate 16. Steccherinum, p. 416. 



Hydnum Linnaeus 



Sporophore cuticular, leathery, corky, woody or fleshy, variable 

 in form, resupinate; pileus, shelving, or bushy branched; hymenium 

 beset with pointed spines; basidia with 4 sterigmata; spores hya- 

 line. 



The species of this genus, between two hundred fifty and three 



hundred, are mostly sapro- 

 phytes but a few are true 

 parasites on woody plants. 

 H. erinaceus Bui.*' 

 Cap 5-30 cm. wide, white, 

 then yellowish or somewhat 

 brownish, the branches form- 

 ing a dense head covered 

 with teeth, fleshy; stem 

 short and stout, 2-8 cm. long 

 and thick, or entirely lack- 

 ing; teeth 3-10 cm. long, 

 slender, densely crowded; 

 spores globose, clear, 5-6 m- 

 The name refers to the ap- 

 pearance of the head. 

 It is the cause of a white rot on many deciduous trees, chiefly 

 oaks. The rotted wood is soft and mushy. Numerous large holes 

 filled with masses of light yellowish fluffy mycelium occur in the 

 heart-wood. Sporophores are often absent on the rotted tree. 

 H. septentrionale Fr.** 

 Sporophores in bracket-like clusters, up to 20-30 cm. wide by 



I''iG. 298. — Fruiting body of Hydnum erina- 

 ceus in a hollow log. After von Schrenk 

 and Spaulding. 



