STEM AND LEAF^, DISEASES 151 



mixture affords the best means of control, but the expense of 

 periodic application has to be faced as a permanent charge unless 

 the humidity of the situation can be reduced. 



Corticium (Pellicularia) koleroga (Cke.) v. Hohn. 



This species occurs on coffee in Porto Rico, Jamaica, Trinidad, 

 Surinam, Venezuela and Colombia, and has been identified with 

 a fungus originally described from Mysore, India. As described 

 by E. A. Burt, the vegetative mycelium forms long, slender 

 mycehal strands of rather uniform diameter, whitish or pallid 

 at first, finally fuscous, running along the branches, and the midrib 

 and veins of the leaves, infesting the leaves and ramifying 

 between the cells of the leaf parenchyma, finally emerging at 

 many points on the underside of the leaf to form minute fructi- 

 fications which give a mottled appearance to the leaf ; fructi- 

 fications soon laterally confluent into a thin arachnoid, perforate 

 membrane covering the under surface of the leaf between midrib 

 and principal veins, drying pale smoke-grey. Spores hyaline, even, 

 flattened or slightly concave on one side, 10-13 X3I-5 microns. 



This species is distinguishable from the preceding by the 

 absence of sclerotia and the thinner, lighter coloured, more 

 firmly attached fructifications, which would seem, moreover, 

 to be much more freely produced. 



On coffee in Porto Rico, according to G. L. Fawcett, this 

 thread blight is common on all plantations except those at 

 higher altitudes, and is conspicuous from the appearance of the 

 blackened leaves held suspended by its threads. It reduces 

 the foliage and often causes the death of twigs. The berries 

 are also attacked, but the loss from this cause is not important. 



The fungus has also been observed in Porto Rico to occur 

 under favourable circumstances on sour orange. Hibiscus, Croton, 

 and two wild vines of the genera Luffa and Cucumis. It has 

 recently been recognised to be rather common in Trinidad on 

 coffee and " croton " (Codiaeum). 



Control. 



The information from Porto Rico is that gathering and burning 

 the diseased leaves gives poor results. Lime-sulphur sprays 

 have proved ineffective. Bordeaux mixture prepared with an 

 excess of lime is effective if followed by inspection and where 

 necessary re-sprapng. 



Horsehair Blight. 



This is the name given to fungus strands, closely resembling 

 black horsehair, forming a loose tangle, with occasional attach- 

 ments, among the leaves and twigs of cacao, nutmeg, and other 

 trees grown under humid conditions. 



It appears from recent investigations by T. Petch that the 



