QUARTERLY CIIROVICLE OF MICROSCOPICAL SCIENCE. 299 



misapprehension Mhich still larj^ely exists as to the real 

 nature of the coffee leaf disease {Hemileia vastairix), and the 

 erroneous views and wild conjectures propagated respecting 

 it, I feel that it is desirable I should again offer some obser- 

 vations on the subject. The disease consists in the parasitic 

 growth within the cofFee-tree of a well-defined species of 

 fungus, originated and reproduced by means of spores, easily 

 identified by employment of the microscope, and thus readilv 

 distinguisliable f^i'ora every other known fungus. There can 

 be no question that this fungus is coraraunicated from coffee 

 plant to coffee plant through dissemination of the spores, 

 and that it may be conveyed by the wind, or by streams of 

 water, or by animals of any kind moving from place to place. 

 The fungus has only yet been detected, in a definitely organ- 

 ised form, in the cellular tissue of the coffee leaf, lying 

 immediately under the diseased spots, in the spores them- 

 selves, and in the filaments produced by the germinating 

 spores. The fungus would appear, however, to be present in 

 the growing tissues generally of the coffee plant in a diffused 

 form, altering the character of the cell-contents, and thus 

 producing the stains observable on the bark of the young 

 branches, and the pale somewhat translucent spots to be seen 

 in the leaves previously to the outbreak of the orange-coloured 

 spores. 



Investigations with the microscope with reference to the 

 germination of the fungus spores have been made by my 

 friend, the Rev. R. Abbay, and by myself. The process has 

 been observed by both of us. Mature spores removed from 

 a diseased coffee leaf and laid upon charcoal kept constantly 

 moist, commence to germinate in a few days. The germi- 

 nation consists in the spore becoming somewhat enlarged, 

 and its contents converted into one or more globular trans- 

 lucent masses. From each of the latter a filament is de- 

 veloped, which grows very rapidly, and becomes more or less 

 branched. At the termination of some of these branches 

 secondary spores are produced in the form of radiating 

 necklace-shaped strings of little spherical bodies of uniform 

 size, and this form closely resembles the fructification of an 

 Aspergillus. Mr, Abbay has also observed another form of 

 secondary spores arranged in single rows of spherical bodies, 

 a good deal larger than those radiately arranged, but still 

 exceedingly minute. These inconceivably numerous second- 

 ary spores may be easily carried by the wind into sur- 

 rounding districts, and thus convey infection to distant 

 plantations. 



The effect of the fungus upon the coffee-tree would seem 



VOL. XIV. NEW SER. U 



