101 



-the planters cut out the Coffee-trees infected by Ti/lenchus, and avoid 

 planting Coffee again on the same ground for several years. In Egypt 

 this disease should be carefully watched, as the Tylenchus might 

 perhaps attack other plants — for instance, the newly cultivated Sugar- 

 Beet. 



Preliminary Report on the nature of the Banana Disease prevalent at 



Alexandria 

 By Dr. Looss and G. P. Foaden. 



Some time since a short report on the external symptoms and pro- 

 bable cause of the Banana disease prevalent near Alexandria was 

 communicated to the Scientific Committee on December 17, 1901, by 

 Dr. Preyer. [This is the paper printed above.] 



In December the writers, at the request of the Alexandria Muni- 

 cipality, visited an infected plantation at Gabarri, where the disease 

 was evidently causing great havoc. In addition to this examination 

 on the spot, portions of leaves, stems, roots, &c, were taken for micro- 

 scopic examination. 



The description given by Dr. Preyer in the article referred to 

 correctly describes the external symptoms of the disease, and mi- 

 croscopic examinations also indicate that his conclusions were cor- 

 rect as far as they went. It is clear that parasitic worms, if they are 

 not absolutely and entirely the c uise of the disease, at least play by 

 far the most important role in bringing it about. They live chiefly in 

 the roots, for on examining the rootlets some little distance from the 

 parent plant it was found that a considerable number of them had died 

 off and were in a state of putrefaction, while others which were still 

 living showed the knobby appearance mentioned by Dr. Preyer ; others 

 again were apparently healthy. On removing the finer particles of 

 earth adhering to the latter their surfaces were seen to be covered with 

 numerous dark dots. These proved to be the places where the young- 

 est terminal off-shoots of the roots branch off from the main rootlets. 

 Some of them were still found in connection with the latter, but almost 

 all were in different stages of decomposition, this evidently starting 

 from the base of the offshoots and eventually leading to their death 

 and disappearance. 



The conclusions which follow have been derived from an examina- 

 tion of these three different aspects of the roots, but the whole trunk of 

 a very diseased plant was also examined together with the entire 

 root system. These main branches of the root did r\ot show, in this 

 case, the knobbed appearance referred to ; a few showed the dotted ap- 

 pearance, but the majority were dead. The number of worms present 

 was considerably fewer than in the secondary roots. As far as an 

 opinion can be expressed on evidence before us, it appears that 

 the secondary roots are particularly singled out for attack, and, becom- 

 ing finallly destroyed, the food supply of the plant is partially cut off, 

 the circulation of the sap is retarded, growth checked, and the exter- 

 nal symptons observed and described by Dr. Preyer are the natural con- 

 sequence. Where putrefaction is going on other minute forms of life 

 are found, and, owing to the favourable conditions present, multiply 

 sX an enormous rate. There were found in the plants examined 

 several species in great numbers of Rotatoria and Infusoria, but all 



