10(J HEART-ROT 



favour their formation arc not always present. l)iit probably 

 the chief reason is that owing to theii' insignilieance they 

 arc generally overlooked. Olsen (Brefcld, 1889, p. J 77) 

 has, however, found layers of the conidiophores on fallen 

 trees in Norwa}^, groAving in such a way as to have a super- 

 ficial resemblance to a species of Corticiufn. He does not 

 state the time of the year at which they were found. This 

 is important, as it is possible that climate plays an important 

 pai-t in their formation. 



Brefeld, who has had imrivalled success in ]H'Ochicing the 

 fi'uctitications of this higher fungi in the laboratory, was 

 unable to stimulate their growth in the case of Fomes 

 annosus, and suggested that under pure-culture conditions 

 a conidial race is produced which becomes incapable of 

 bearing fructifications. In one of my own cultures, how- 

 ever, a sterilized larch block, which was infected with 

 conidia, produced normal, -though small, fructifications 

 (fig. 44), and it must be presumed that Brefeld did not 

 expei'iment with the most suitable medium. 



The germination of conidia is in every way similar to 

 that of basidiospores. They germinate at once, and with 

 great regularity, both in pure water and in nutrient solu- 

 tions. The possibility of making inoculations from old, 

 api)arently (hied up, cultures of more than a year's standing- 

 testifies to the longevity of the conidia. 



Pure cultures on artificial media. ( ultures of the fungus 

 grow readily in 15 per cent, gelatine oi- 3 i)er cent, agar-agar 

 when appropriate food-stuffs are added. I have fountl that 

 meat extract 0-3 per cent., malt extract 3 per cent., give 

 suitable nutriment. If the medium is at all alkaline it may 

 be neutiali/cd with citric acid. CiiHiires were liist obtained 

 tioiii lotted j)ortions of puni|)e(l trees. Small lumj)s of 

 wood wei'c sterilized externally by holding for a few seconds 

 in a weak flame. The centi'al portions were then cut out 

 with a stcj'ilized knife and ])laced on the gelatine in cultui'e 

 llasks, which had been suitably sterilized ])rior to inocula- 

 tion. Cultures grew .slowly at first and thiii fairly rajndly, 

 and were similar on gelatine and agai'. The mycelium is 



