PINE DISEASES 289 



tion that the seciospores cause the infection of the leaves of 

 species of oaks instead of the currant and gooseberry. Some 

 investigations point to the possibility that this fungus may 

 be an exception to the rule in requiring the presence of 

 the oak in order to have the infection of pines occur. This 

 fact, together with the conditions observed in California and 

 Oregon when the pines are often infected with no oaks near, 

 leads to the supposition that the oak may not be neces- 

 sary in the life cycle. Likewise, the fungus persists over 

 winter on the evergreen oaks on the Pacific Coast. The leaves 

 harbor the mycelium and new fruiting-bodies are developed 

 in the spring around the dead areas produced the previous year. 

 The destructive action of the fungus on pines is caused by 

 the flow of resin from the diseased tissue into the conducting 

 tissue of the branch and trunk. This shuts off the food and 

 water supply and causes the death of the parts above. The 

 affected bark of the enlargement dies after a few years and 

 insects and wood-rot fungi enter at these places. 



Control. 



Where oaks and pines grow in close proximity, the control 

 of this disease may be accomplished by eliminating the oaks, 

 unless it is definitely proved that the oak is unnecessary in the 

 life history. The elimination of the trees showing one or more 

 galls of this disease is advisable at the time of cutting. 



References 



Weir, J. R. Observations on the pathology of the jack pine. U. S. 



Dept. Agr. Bui. 212 : 1-10, pi. 1, figs. 1-4. 1915. 

 Graves, A. H. Notes on diseases of trees in the southern Appalachians 



II. Phytopathology 4 : 5-10, pi. 2, fig. 1. 1914. 

 Meineoke, E. P. Peridermium Harknessii and Cronartium Quercuum. 



Phytopathology 6 : 225-240, figs. 1-2. 1916. 

 Hedgcock, G. G., and Long, W. H. Identity of Peridermium fusiforme 



with Peridermium cerebrum. Jour. Agr. Res. 2 : 247-249, pi. 11. 



1914. 



