314 THE COFFEE-LEAF DISEASE. 



Iii the absence of fruit it is impossible to say whether the place 

 of this plant is in the present section or in § Harniera. 



No. 5093 (clistr. Pungo Andongo) may perhaps be a larger form 

 of this with leaves hairy on the underside. 



(To be continued.) 



THE COFFEE-LEAF DISEASE. 



[Mr. Marshall Ward's Preliminary Report on the Ceylon 

 Coffee-leaf disease presents several new and important phenomena 

 in the life -history of Hemileia vastatrix. Of even greater interest, 

 we venture to think, at this stage of the investigation than these 

 facts are the evidences given by the Eeport of the thoroughness of 

 the methods which Mr. Ward is employing. The difficulties to be 

 met with in any research of this kind cannot easily be over- 

 estimated : one of the most troublesome and misleading is the 

 presence of foreign fungi. In Europe such at least as commonly 

 occur have become more or less familiar, and their connection with 

 the subject of investigation is easily determined ; but Mr. Ward has 

 to contend with unfamiliar forms (both, apparently, special parasites 

 of the coffee -plant and more generally- distributed fungi), all of 

 which must be thoroughly traced, as they may possibly be phases of 

 the Hemileia. Mr. Ward recognises this difficulty, and is actively 

 meeting it ; and we may now hope in due course for details of the 

 life-history of this highly interesting fungus. That part of Mr. 

 Ward's Report which describes his examinati 



appended.— G. M.1 



examination of the Hemileia is 



Specimens of disease -patches in all stages were selected. Some 

 were very small, hardly yellow "pin-spots," only seen when held 

 up to the light ; others older, larger, and more oily-looking ; still 

 older ones were covered below with the yellow or orange "rust" ; 

 while yet further advanced irregular patches presented brown or 

 black blotches in the central part, the yellow powder being at the 

 edges. 



The microscope establishes the following facts, and I have 

 confirmed the observations since by examination of specimens from 

 all parts of the coffee- districts, at various elevations and seasons. 



Thin slices of the " pin-spots " and pale yellow patches, taken 

 in all directions, and examined fresh or treated with chemical 

 reagents, show that this part of the leaf has the passages between 

 its cells which lead to the exterior blocked up with a much- 

 branched, tubular, coral-like mycelium; the short, stumpy branches 



course 



wans oi tne cells. The contents of the tubes are very granular auu 

 oily, usually coloured by a pigment varying from yellow to deep 



orange-red. 



The older patches present similar features exaggerated, but the 

 branched tubes of the mycelium have sent peculiar groups ol 

 processes outwards through the outlets (stomata) of the epidermis; 



