u6 



tudinal and transverse sections. At once it was noticed that the 

 cortex of the roots was abnormal. 



In a diseased root, the walls of the cortex cells appear to be 

 shrunken and the cells are turgid no longer. Between the walls 

 of consecutive cells can be seen large dark-coloured septate 

 threads of a fungus mycelium,* while many of the cells themselves 

 have become invaded by the same. When a cortex cell is threat- 

 ened by the approach of a fungal thread, its cell contents appear 

 to be altered, for large yellowish globules make their appearance. 

 Whether these have been produced by the cell itself as a means 

 of protection against the fungus, or whether they are the result of 

 decomposition could not be determined, but after the mycelium 

 has gained an entrance into the cell, these globules as well as all 

 the other cell contents, are destroyed and absorbed. 



The mycelium of the fungus spreads from one cell to another 

 by piercing through the cell walls, and soon obtains an entrance 

 into the thin-walled cells of the central cylinder and eventually 

 into the vessels themselves. 



The red discoloration of the stem was carefully examined 

 microscopically but except in the case of trees that were very 

 badly diseased, few mycelial threads could be detected. These 

 in the advanced cases were similar to those noted in the roots, 

 but I am of opinion that the red discoloration is primarily clue to 

 the disorganization of normal changes in the stem through the 

 stoppage of supplies from the roots, rather than to any effect of 

 the small amount of fungal mycelium found in diseased stems. 



PETIOLES. — It was observed that almost without exception, the 

 petioles of the leaves of badly diseased trees showed a large num- 

 ber of minute ruptures of the epidermis, after they had died and 

 had fallen to the ground. The petioles in varying stages of 

 disease were therefore submitted to a careful microscopic examin- 

 ation and it was observed that a mycelium of a fungus was found 

 in all diseased petioles. 



The point of the first attack could not be determined, but it 

 would appear that the petiole, just where it expands to ensheath 

 the stem of the tree, is the part where tlie effect of the fungus is 

 first noticed. The whole petiole gradually assumes a blackish 

 colour, the leaflets become brown, and eventually on the dead 

 petioles minute ruptures take place in the epidermis of the petiole 

 just where it begins to expand before joining the stem. These 

 give off a black powdery dust, which consists of spores of two 

 kinds— one, single-celled and colourless, and the other two-celled 

 and brown. 



1 6. The two-celled spores suggested that the fungus belonged 

 to the genus Botryodiplodia and therefore specimens were forwarded 

 to Dr. N. Patouillard, who has recently described several new 

 specimens of fungi on coco-nuts from French Polynesia, for iden- 

 tification and he reports as follows : — 



*The mycelium of a fungus is made up of minute threads or filaments and may be 

 looked upon to bear a similar relation to a whole fungus as the roots of a coco-nut 

 bear to the whole palm. 



