182 EEY. R. ABBAY ON HEMILEIA VASTATRIX. 



the cellular mycelium or conidia of Hemileia ; but I have never 

 been able to determine whence they came. 



Two points of difference between the Ceylon and the Sumatra 

 forms of Hemileia vastatrix are noticeable: — (1) the transparent 

 bodies, like barren cysts, which are found growing along with the 

 sporanges in the Sumatra specimens, but which are never seen on 

 those from Ceylon ; (2) the greater tendency in the cells of the 

 mycelium of the former to bulge out and form comparatively 

 large ovoid masses. This is much less marked in the Ceylon spe- . 

 cimens. In other respects, as far as I am able to judge, they are 

 alike. It is believed that under somewhat different conditions 

 the red sporanges are capable of giving rise to a different form ot 

 mycelium from that already described ; but as the observations 

 on this point were made with a low power, I have thought it best 

 to omit noticing them here. 



rf Growth, &c— With 



He 



to infect growing coffee-plants, both through their young and 

 their fully formed leaves. The same has been tried with coffee- 

 leaves placed in an atmosphere saturated with moisture and kept 

 at a constant temperature of 90° F. ; but in no case has the 

 attempt succeeded, although the sporanges, the growing myce- 

 lium, and the conidia have been placed on the leaves. What the 

 necessary conditions are which are absent it is difficult to ima- 

 gine, unless it be that the stomates, through which alone appa- 

 rently the fungus finds its way into the leaf, are too contracted 

 under the artificial conditions applied to allow the mycelium fila- 

 ments or the spores to enter. The conidioid form of the fungus 

 may readily be grown on the outside of the coffee-leaf in a moist 

 atmosphere; but it does not appear to penetrate into the leaf ; 

 for in the case of such plants I have never seen either the myce- 

 lium within the tissues of the leaf or the clusters of red sporanges 

 outside it. This latter form — the common one by which the 

 " disease " is recognized in Ceylon — I believe to be the dry- 

 weather form of the fruit, appearing generally in its greatest 

 intensity soon after the rains have ceased, but very rarely during 

 their prevalence. During the prolonged wet season the conidia 

 have been found growing on many other plants as well as on the 

 coffee-tree ; but the mycelium remains on the outside, and the 

 leaves show no traces of the disease. If it is necessary before 



