60 Sphaeronema sjj. 



tained these globules sometimes in great abundance, some of the cells 

 being full of them. No trace of these could be seen in the cultures on 

 artificial media, they are not present either in recently infected, or 

 normal healthy cortex. Tissue which had been killed and partially 

 destroyed by the Sphaeronema formed then a suitable nidus for bacteria 

 which were present in abundance. One case of inoculation on a stripped 

 surface which was kept under observation proved very interesting. 



The surface was inoculated 27/11/18 and six days later pycnidia 

 appeared. In the meantime the mycelium had spread over the entire 

 surface exposed (about 24 square inches). 



Cultures were made from pycnidiospores and the surface was then 

 left, i.e. no fungicide was applied. 



By 28/12/18, approximately a month later, healing from the edges 

 had made fair progress and a month later still the wound appeared to 

 be in a fair way to recovery. 



More cortex was removed 2/2/19 both above and below but in con- 

 tinuation with the part previously exposed, and in less than four days 

 there was the usual appearance on these stripped surfaces showing that 

 the disease was spreading. In eight days pycnidia appeared on these 

 newly exposed surfaces and examination of portions of wood in sections 

 from the original surface showed that the mycelium had penetrated -|" 

 and was then spreading slowly in a vertical direction. 



Other cases similar to the above inoculated 5/12/18, and treated with 

 an antiseptic cover, but in which no further surfaces were exposed, have 

 now almost completely healed over. The cortex shows no signs of 

 disease (9/1/20) and there is every appearance of complete recovery. 

 Regeneration from the sides will however give a very uneven surface 

 to tap over. 



During wet weather pycnidia are produced in abundance on the 

 affected surfaces while resting spores are not at all common. In some 

 cases where the disease proved most difficult to keep in check during 

 a prolonged spell of dry weather, no pycnidia were produced, but 

 immense numbers of resting spores were formed on the surface and some 

 were also found embedded in the tissue several cells deep. Under those 

 conditions it is probable that the resting spores provide an even surer 

 means of distribution than the pycnidiospores and these as well as those 

 in the tissue are equally dangerous so long as tapping is continued, the 

 knife then being the chief agent in their distribution from tree to tree. 



The pycnidiospores are quickly killed by desiccation but the resting 

 spores can withstand this for quite a long time. 



