F. T. Brooks and A. Shakples 71 



The incrustation retains its vitality for a considerable time and, as 

 stated above, it cracks into small pieces as it gets older, and these, 

 breaking away, may be carried to other trees in one or other of the ways 

 mentioned. 



A species of Nectria is often associated with cases of Pink Disease 

 of long standing, but as far as is known at present it is purely sapro- 

 phytic and develops only after the bark has been 'killed by Corticium. 



Pure Cultures of Corticium salmonicolor. 



At the beginning of these investigations efforts to obtain pure 

 cultures of the fungus were unsuccessful. We soon recognised that the 

 incrusting form was usually sterile so we gave up attempts to obtain 

 a deposit of basidiospores with which to start pure cultures. Failing 

 basidiospores, small pieces of the pink incrustation were cut out with a 

 sterile knife and placed on slants of salep agar. The fungus quickly 

 developed, but the cultures were usually contaminated. Subcultures 

 started from these were eventually obtained which were probably pure. 

 No further attempt to obtain pure cultures in this way was made 

 because at this stage one of us obtained material in the field which 

 appeared somewhat unusual at the time. This material bearing 

 orange-red pustules was sent to the laboratory and immediately 

 examined, when the pustules were seen to consist of masses of spores, 

 these being the Necator form of the fungus which was subsequently 

 obtained frequently. 



Pure cultures were obtained from the Necator spores. These were 

 teased out on sterile glass slides ; some were placed in damp chambers 

 on salep agar, others directly on test tube slants of the same medium. 

 The spores quickly germinated in the damp chambers (Fig. 10) ; these 

 were kept under observation for three or four days in order to see 

 whether the cultures remained pure. After this, transfers from the 

 damp chambers to test tube slants were made. As these cultures and 

 those obtained by placing spores on test tube slants direct were identical, 

 little doubt remained as to their purity. The mycelium was pure white 

 and did not grow copiously. After a period of about ten days a faint 

 pink colouration appeared in the cultures. The agar cultures were 

 kept for several weeks, but no further development took place. Other 

 cultures were then made by transferring small portions of the mycelium 

 to blocks of sterilised Hevea wood placed in tubes (a figure and explana- 

 tion of the form of tube used is given in Fig. 11). About 50 per cent. 



