CHAPTER Vl 

 HEART-ROT. FOMES ANNOSUS (Concluded) 



Reprodiu'tivp organs : fructifications ; conidiophores. l^inv cultures 

 on artificial media, ("nltures on natural media. Infection experiments. 

 Mode of attack in nature. The frefpiency of heart-rot in ])lantations 

 which form the first rotation on cultivated soil. IMethods of ])revention. 



lU'produetlye organs. Fomes annosns has two Idncls of 

 reproductive organs. These are (1) fructifications, nsnally 

 large, of Pohjporus form, which may occasionally be found 

 associatcxl with larch heart-rot, but which are nuieh com- 

 moner on young trees of other coniferous species when 

 they have been killed by the fimgus ; and (2) conidia on 

 somewhat specialized conidiophores, which occur regularly 

 in all cidtures, but have been found, so far, only very rarely 

 in a truly wild state. They are apparently formed only in 

 a sat\u'ated atmosphere, such as is provided under usual 

 cultural conditions, but which cannot be relied upon in 

 iiatiii'e. 



'J'he morphology and life-history of the fungus have been 

 carefully woi-kcnl out by Brefeld (18S9) under the name of 

 Heterobasidion annosum, (Fries) Brefeld, and I have made 

 free use of his descrii)tion in the following accoiuit. 



1. Typicul frucfificfi lions are shown in figs. 29, 30, 39, 4(1. 

 They are of two kinds — bracket-shaped, borne usually on 

 the sides of trunks and above ground, and ' resupinate \ 

 which grow on the imder-sides of roots and have the w hole 

 or nearly the whole of the upper side attached to the root. 

 The latter form is generally s\d)terranean, and has its lower, 

 spore-bearing side exposed in some hole in the ground, 

 such as those made by rabl)its and mice. 



The fi-uctifications iij'st arise as small white masses of 

 hyphae, often no bigger than a ])in"s head. These break 

 through tlie hark of the roots and broaden on the surface 



