juiyis, 1920 Relative Susceptibility to Citrus-Canker 361 



(e) The sour lime tested proved to be somewhat resistant. 



(/) While the citrons are easily infected, the spots are small and increase 

 slowly in size. Twig infection is not common. 



{g) Citrus mitis, while showing some resistance, is more susceptible 

 than has been reported from the Philippines. 



Qi) The Kansu (Yuzu) orange has proved somewhat resistant. No 

 twig infection has occurred, and only scattering spots have developed on 

 the foliage. 



{i) All numbers of Citrus nobilis and its varieties have proved to be 

 rather resistant to canker. 



(4) All hybrids are attacked by citrus-canker in varying degrees. 



(a) The citranges, citrumelos, citradias, citrandarins, citrunshus, and 

 cicitranges, all having Poncirus trifoliata as one parent, are extremely 

 susceptible. Apparently all crosses with P. trifoliata will yield hardy 

 but susceptible hybrids. 



(6) The citrangedins, citrangarins, citrangumas, and citrangequats, 

 with susceptible citranges as one parent, are not only hardy, but decidedly 

 resistant to canker; in fact, the citrangequat is practically immune in 

 spite of the fact that it is a rapid grower. 



(c) The limequats and orangequats are somewhat susceptible. 



{d) lyimelos and orangelos are as susceptible as grapefruit, while cle- 

 melos, siamelos, satsumelos, and tangelos are not so resistant as the 

 mandarin oranges. 



{e) The calarins and calashus are as resistant as either parent, while 

 siamors and bigaraldins are susceptible. 



(5) All false hybrids are extremely susceptible. 



(6) Leaf texture is apparently an important factor in influencing 

 resistance to Pseudomonas citri by its host plants. This phase deserves 

 further investigation. 



LITERATURE CITED 

 (i) JEHLE, R. A. 



1917. SUSCEPTIBIUTY OF NON-CITRUS PLANTS TO BACTERIUM CITRI. In PhytO. 



pathology, v. 7, no. 5, p. 339-344- 3 ^g- 



(2) 



1918. SUSCEPTIBILITY OF ZANTHOXYLUM CLAVA-HERCULES TO BACTERIUM CITRI. 



In Phytopathology v. 8, no. i, p. 34-35. 



(3) Lee. H. a. 



i918. further data on the citrus canker affection of the citrus species 

 AND VARIETIES AT LAMAO. In Philippine Agr. Rev,, v. 11, no. 3, p. 

 200-206, pi. 9-15. 



(4) 



1918. FURTHER DATA ON THE SUSCEPTIBILITY OF RUTACEOUS PLANTS TO CITRUS- 



CANKER. In Jour. Agr. Research, v. 15, no. 12, p. 661-665, pl- 60-63. 

 (s) and Merrill, R. I. 



1919. The susceptibility of a NON-RUTACEOUS host TO CITRUS CANKER. In 



Science, n. s. v. 49, no. 1273, p. 499-500. 



