THE COFFEE - 



DISEASE. 315 



on reaching the exterior, the ends of these branches form swellings 

 which soon become filled with deep orange-coloured pigment and 

 granules, and the groups of bodies seen from above present the 

 appearance of rosettes. Since these bodies are easily rubbed ^ off, 

 they form a powdery mass on the outside— the so-called "rust." 



Similar examination of the brown or black central blotches 

 shows that the leaf-cells have lost most of their contents, turned 

 brown, and collapsed; thus the upper and lower surfaces come 

 closer together, and such parts are thinner than the rest of the 

 leaf. Usually, a number of black dots are seen on the upper and 



lower surfaces. 



iuvver sunauea. 



There can be no doubt that the tubular branched mycelium 

 has been feeding upon the contents of the leaf-cells, turning the 

 green colouring-matter and other substances into the granular and 

 oily masses found within it, and finally passing forth into the 

 bodies forming the " rust "-powder ; and when we reflect upon the 

 immense quantities of matter thus derived and thrown off from the 

 leaves, we may understand in some measure the terrible enect 



produced upon the coffee plant. 



Some of the yellow "rust" was placed in water ona glass 

 slide, and examined under the microscope. Each "gram 01 tiie 

 powder is a hollow case, somewhat kidney-shaped in longitudinal 

 section, and triangular, with one angle downwards, in transverse 

 section ; it is narrower at the end attached to the mycelium. Ihe 

 upper curved side is studded with papilla or wart-like projections 

 of its outer, colourless coat; the two smooth sides converge .below 

 to a rounded longitudinal ridge. Such a figure exhibits yaiious 

 forms if projected in different positions. As said, tins papillate 

 body has granular orange-coloured contents. 



Many of them soon swell in water, and beco me M ^ 

 globules of clear fluid (vacuoles) from the "P* «d»pri mtnb tmn 

 of water; the papillate body now appears as if •gjJ^gJ^S 

 clearer bodies embedded in the coloured mass. These globules are 

 not always equal in size, but generally are nea r y so I 11 d avei age 

 one-tenth to one-eighth the diameter of the whole ma not only 

 by their appearance, refusal to absorb s tain ,ng : eage nts and 

 general behaviour, but by the fact that they n jde to 

 disappear and reappear 1 am convinced of their fluid natuie 



Others of the papillate ^dies however do no hU^vffdi 

 globules, but swell, and soon lose their "*" «^*?^ 

 contents become very granular and gre y J^W, *£?. J^ See 

 varying from a few hours to a much l «««£ r ?^5^^ 

 which are very minute and numerous pass into a Btateofviolen 

 motion to and fro in the fluid contents of the P*l f ° ■££ 

 This motion is too active to be merely P^L^ *£ £J 

 observed too often to be accidental. Alter "^2^™^ 

 for some hours, the granules pass out into the smio u dmg * ater, 



and become widely distributed, ^..^Jffi 11 " 

 behind ; their ultimate fate is not yet satisiacto iUj est. * he d. 



A piece of leaf, with "rust" on it, was ex posed to «,,« £ and 

 was found to become paler. Examination showed that the majonty 



