.\t)TK ON rODI'ORL'S I.UCIDIS LKVSS. 513 



the now colliilosc walls. This digestion is shown in h'is^ O. where 

 the walls hordcrinij^ iho Inniina of the wood proscnchxina are 

 corroded and oellnlose plates project into the Inmina. This 

 delio-nitication and al)Sor])tion result in the cell walls hecoming 

 thinner and thinner, ihoutih the middle lamellae are evidently 

 acted ujx)n with some difficulty. W'hen this, too, is delig;nihed 

 and ahsorbed, the destructit)n of the cell is complete. I have 

 not observed any delignihcation in the large vessels. 



The action of the fimgus on the willow resembles somewhat 

 the destruction of the wood cotton-wood by Fomes applauatus, 

 as described by Heald,* but the deligniiication and digestion 

 would ap{)ear to be both slower and more gradual than that 

 caused by the latter fungus. 



Though of necessity there must be a certain amount of 

 disorganisation of the wood cells, nevertheless in the material 

 examined I have not noticed any particular tendency on the 

 part of the ifiuigus to form pockets or cavities filled with fungoid 

 hy]:hse. The white mottled areas are due to a combination of (a) 

 delignification ; (b) the presence of hyalin which fills the vessels 

 and medullary rays, especially the former. 



It is further of interest to note that the medullary rays of 

 the willow are attacked by the solvents of this fungus only at 

 a late stage — in fact, their action on the rays was almost over- 

 looked. 



Fate of Attacked Trees. 



It was on the willow tree already referred to that 1 was 

 able somewhat to follow the ultimate fate of attacked trees. 



When first observed, this tree had three sporophores on 

 the roots and nine on that side of the stem (Plate 145) on 

 which, higher up. were a few dead branches. On the opposite 

 side there were a few young sporophores on the stem and roots, 

 but this side was to all intents and purposes more active and 

 \igorous, and had more life in it than the first mentioned. 



Five months after, when I ag'ain happened to visit the place, 

 the tree was nearly dead, and it is probable that by now the 

 fungus has killed it. 



There is little doubt that the death of a large number of 

 the Acacia trees around Pretoria must be attributed to this 

 fungus. Here, unfortunately, the host was always dead when 

 the sporophores were found, and further investigation w'as 

 imjjossible. 



Control. 



The fungus, which is a facultative parasite, forms sporo- 

 phores abundantly after the death of its host, and methods of 

 control should be directed towards preventing the spread of the 

 disease. Allowing diseased trees, or dead logs or roots har- 

 bouring the fungus, to stand or lie in plantations is a sure 

 rneans of propagating the fungus, and thus rendering trees 



* Heald, F. D. : " A Disease of Cottonwood caused by Efvingia mcga- 

 lonia Xcbr.," Agric. Experiment Station Ann. Rep. (1905), 92. 



