Dec. 23, 19x8 Susceptibility of Rutaceous Plants to Citrus-Canker 663 



Table I. — Summary of results of inoculations on plants of Rutaceae — Continued 



Field observations corroborating these inoculation data have been 

 made in many cases. Thus, in South China Severinia buxifolia occurs 

 naturally, exposed in a number of instances to infection from Citrus- 

 canker in near-by orchards. In no instances were lesions in any way 

 resembling those of Citrus-canker found. Aegle marmelos and Triphasia 

 trifoUa are cultivated at Lamao in the Philippine Islands, surrounded by 

 nursery rows of Citrus trees heavily infected with canker. In no case 

 have lesions similar to those of canker been found on these hosts. 



Chalcas exotica is a commonly-grown ornamental in Manila; nothing 

 at all resembling Citrus-canker has ever been found occurring naturally 

 upon it, although sources of infection are in some cases closely present. 



Xanthoxylum rhetsa and A talantia disticha occur naturally at L-amao in 

 places where infection with Citrus-canker would be easily possible. No 

 lesions similar to canker have been found on these plants. 



Fortunella japonica occurs in orchards at Lamao and also at Los 

 Banos, Philippine Islands. No naturally-occurring cankers have ever 

 been seen on this host. Wolf ^ reports Citrus-canker on kumquats, but 

 does not mention what species were under observation. Swingle ^ also 

 reports canker on kumquats in Japan. 



Fortunella japonica, although susceptible to Citrus-canker under the 

 most optimum conditions, should nevertheless be regarded as highly 

 resistant, closely approaching immunity. 



On the other hand, Foriumila hindsii occurring naturally in South 

 China has been observed frequently with heavy canker infection. Plants 



• Wolf. Frederick A. citrus-canker. In Jour. Agr. Research, v. 6, no. 2, p. 70. 1916. 



' U. S. Department op Agriculture, citrus canker in phiuppines. In U. S. Dept. Agr. Dcpt. 



Circ, v. I, no. i, p. 8. 1915. 



