THE FUNGI WHICH CAUSE PLANT DISEASE 437 



usually brownish during the growing season from the covering of 

 conidia; margin obtuse, broadly sterile, white or slightly cremeous, 

 entire to undulate: context corky, usually rather hard, zonate, 

 fulvous to bay, 5-10 mm. thick, thinner with age; tubes very 

 evenly stratified, separated by thin layers of context, 5-10 mm. 

 long each season, avellaneous to umbrinous within, mouths circular, 

 5 to a mm., whitish-stuffed when young, edges obtuse, entire, 

 white or slightly yellowish to umbrinous, quickly changing color 

 when bruised: spores ovoid, smooth or very slightly roughened, 

 pale yellowish-brown, truncate at the base, 7-8 x 5-6 fi. 



It is described by Heald °* as the cause of rot of both heart and 

 sap wood of living cotton-wood trees. The invaded medullary 

 rays first lose their starch by digestion. Next the lignin is dis- 

 solved, then the cellulose. 



Von Schrenk regards this fimgus as a saprophyte since it grows 

 usually only on outer sap wood that is dead and so far as he ob- 

 served, it does not cause a true disease. 



F. ulmarius Fr. is injurious to elm. 



F. semitosus Berk, causes root rot of Hevea in India. 



F. australis Fr. is a wound parasite on Acacia in Ceylon.*^^ 



Trametes Fries (p. 417) 



Sporophore annual, rarely perennial, sessile; context homo- 

 geneous, coriaceous to corky, extending between the tubes, which 

 are circular or irregular. 



There are about one hundred forty-five species. 



T" • • /rr<l_ \ T7 S5, 74, 78, 79 



T. pmi (Thore) Fr. ' ^ ' 



Pileus hard, woody, typically ungulate, conchate or effused- 

 reflexed in varieties, often imbricate, 5-8 x 7-12 x 5-8 cm., smaller 

 in varieties; surface very rough, deeply sulcate, tomentose, tawny- 

 brown, becoming rimose and almost black with age; margin rounded 

 or acute, tomentose, ferruginous to tawny-cinnamon, entire, 

 sterile in large specimens: context soft-corky to indurate, homo- 

 geneous, ferruginous, 5-10 mm. thick, thinner in small specimens; 

 tubes stratified, white to avellaneous within, becoming ferrugi- 

 nous at maturity and in the older layers, 5 mm. long each season, 

 much shorter in thin specimens, mouths irregular, circular or 

 dsedaleoid, often radially elongate, averaging 1 to a mm., edges 



