i62 Transactions British Mycological Society. 



of oil. They occur also on the surface of the wood, and in that 

 position are indistinguishable from those of Grevillea. The hyphae 

 in the smaller roots are typically Rhizocionia-\ike, and permeate 

 the host tissues very thoroughly. Clamp-connections and 

 chlamydospores, neither of which have been seen in tea root 

 sections, are common. Black sclerotial plates occur only in the 

 driest and presumably earliest-infected roots, but hyphae are 

 plentiful in the wood of the collar of the tree. The plates are 

 of the usual structure, and they give off branch hyphae which 

 leave the parent mycelium at the usual right angle and penetrate 

 the surrounding tissues. On the larger roots, the mycelium of 

 the fungus is most plentiful in and near the cambial tissues, 

 in which position it forms thin continuous sheets resembling 

 the black plates and also the growths of the Grevillea fungus 

 on filter paper. These sheets cling closely to the inside of the 

 detached bark. In all three cases, Grevillea, tea, and Bixa, the 

 hyphae of the Rhizoctonia have been observed to make little 

 use of pits in their passage through the tissues, but penetrate, 

 apparently without difficulty and doubtless by the action of one 

 or more enzymes, all obstructing cell-walls. The cell-cavities 

 throughout the wood of diseased roots of tea and Bixa are 

 frequently filled with gum, a condition recalling that found in 

 the roots of Grevillea. 



The Bixa fungus has been isolated from root fragments and 

 grown in the same media as the tea and Grevillea forms. After 

 thirty-six hours, the young hyaline mycelium shows the typical 

 form and method of branching. The hyphae then measure up 

 to 8 /i in diameter, and are often aggregated into strands of 

 from two to six or eight threads. Further developments follow 

 the lines already described. 



The Rhizoctonia on Coffea robusta and 

 Casuarina equisetifolia. 



The Rhizoctonia was subsequently discovered on Coffea robusta 

 and Casuarina equisetifolia. These cases differ from those of the 

 tea and arnatto inasmuch as none of the affected plants — and 

 examples of the root diseases of each have been obtained from 

 different localities — had been growing in close proximity to 

 either healthy or diseased Grevillea robusta. The infections are 

 not only independent of Grevillea but also of each other, and 

 they establish a suspicion that the Rhizoctonia is unlikely to be 

 confined to the first host on which it was found or to the tea 

 and arnatto to which it has seemed to spread. All the new cases 

 have occurred on European coffee estates which are in good 

 order. The Coffea robusta is planted in the usual way in plots, 



