248 



to be a species of Corticiuni or Hypochnus. It takes the form of white 

 threads which run over the surface of the branches and leaves causing 

 the younger parts to wither and die : — its effect is not unlike that of a 

 bacterial blight. The disease is spread by m'::'ans of dead leaves which 

 are blown and lodge against branches, and by the passage of the 

 threads from one branch to another in contact with it, The disease, 

 which was present in small amount, was got rid of by pruning off 

 shoots which possessesd the threads and by burning them together 

 with all leaves and twigs which had fallen from the trees. A spraying 

 method of treatment is also applicable in this case. 



Leaf Diseases. — Pestalozzia Guepini, Desm., and Phyllosticta 

 Hevea, Zimmermann, have been observed to cause spots on the leaves, 

 more especially of iseedlings. They are few in number and are at 

 present not of any economic importance. Pestalozzia Guepini has not 

 yet been observed to attack the stems of seedlings as is said to occur 

 in Ceylon. The plant sheds its leaves and renews them readily ; by 

 this habit it possesses a strong power of resistance to leaf diseases. 



Physiological Effects. — The penetration of the tap root into 

 acid soil or into a heavy, impenetrable clay bottom results in the 

 checking of the growth of the tap root and the rapid shedding of the 

 leaves. The plant, however, responds by expension of the lateral and 

 more superficial roots, and recovers. This occurs on peaty soils and 

 on soils with a heavy clay bottom. The plants grown on such soils 

 possess little or no tap root and are easily blown over by wind. 



Other Effects. — Burrs occurs in some quantity more especially 

 on old trees. They are referable to two distinct causes. In the one 

 case they are due to the development of an excess of "wound wood " 

 at points where the knife is allowed to wound the wood tapping ; in 

 the other case they are apparently stimulated by bad tapping, but 

 also occur on untapped trees in small quantity. Those of the first 

 type are prevented by avoiding the wounding of the wood in tapping; 

 while those of the second type, which may attain dimensions measur- 

 able by feet and may necessitate the transference of the tapping 

 surface to the upper portions of the trunk, must be removed early 

 when they are young and pea-like and before they fuse up with the 

 main wood. 



Examples of Fasciation, which consists in the development of 

 strap-shaped structures, produced by the fusion of stem and leaves, 

 and which may take the form of antlerlike structures, sometimes 

 occur, though they are rarely met with. 



DISEASES OF ROBUSTA COFFEE. 



Leaf Diseases. — Hemileia vastatrix, Berk, and Broome, which 

 was originally supposed to produce little or no disease in robusta 

 coffee, has been found to be as prevalent on that plant as it 

 is on Liberian coffee. In introducing a disease-resisting species 



