58 Sphaeronema sp. 



outer surfaces in all cases had been completely killed. Species of 

 Cephalosporin™, Fusarium, etc., were gradually covering the whole with 

 white mycelium, and bacteria were completing the work of destruction. 

 Portions of infected bark and wood were examined microscopically after 

 48 hours and again after six days. The mycelium had in places pene- 

 trated to a depth of T V~s inch, apparently penetrating most deeply 

 along the medullary rays and then spreading laterally more slowly. 

 Even in cells almost filled with mycelium, the nucleus in some cases 

 was still present and apparently unaffected after six days, but in most 

 cases, of the cells attacked, the contents had disintegrated or entirely 

 disappeared. In the bark, cells containing tannin were also attacked. 

 A few characteristic fruits (pycnidia) had developed by the end of the 

 fifth day and quite a large number in six days, the surface where these 

 appeared having turned quite black. 



A mass of spores just emerging from the apex of a pycnidium was 

 carefully removed on sterilised needles, the operation being conducted 

 with the aid of a high power lens ; the moulds present, Cephalosporium, 

 Fusarium, etc., were as far as possible excluded and inoculations made 

 on agar and on fresh bark sterilised outside with picro-f ormal, and then 

 placed straight from the tree into sterilised tubes. 



The bark showed the typical brown discolouration round the point 

 of inoculation at the end of 24 hours. 



One of these pieces of bark after six days growth was sterilised in 

 1/500 corrosive sublimate solution, then washed with freshly boiled dis- 

 tilled water, and finally the upper (previously infected surface) being 

 the original inner surface of the bark shaved off with a freshly sterilised 

 chisel. A second shaving was then taken from the surface newly exposed, 

 this presumably contained active pure mycelium, and in fact such proved 

 to be the case, as on being brought into contact with clean bark fresh 

 from the tree, the characteristic colouring was apparent in 18 hours, 

 while the controls remain unaltered. In every case of successful inocu- 

 lations, the attack spread with quite remarkable rapidity. 



CULTURES. 



Cultures were set up from spores removed from pycnidia produced 

 on bark as above, on Prune agar, 2 per cent, virol agar, Quaker oat agar, 

 agar made with infusion of rubber tree bark, and in every case pycnidia 

 were produced in abundance in from five to nine days. Similar cultures on 

 sterilised wood produced an abundance of pycnidia and also resting spores 

 in from 10-15 days. Cultures on 2 per cent, cane sugar agar gave very 



