Aug. 26,1918 Susceptibility and Resistance to Citrus-Canker 
347 
Citrus nobilis Lour. “Naranjita”? (CPB 7830, seedling), II. 
The leaf characters of this plant resemble those of the Satsuma. 
Although the plant (14 inches) has ben in fairly good condition for infection, only 
one small Citrus-canker spot has developed. It will be tested again, as it gives some 
promise of being resistant to canker. 
Citrus nobilis var. unshiu Swingle. Satsuma (budded on Poncirus trifoliata, Ala¬ 
bama), II. 
Although the plant (36 inches) has not been in good condition for infection, Citrus- 
canker has developed on a number of leaves. However, infection was not severe and 
caused no defoliation or apparent injury to the leaves. 
The spots (PI. 52, E) are few in number, small, brown, raised, compact, with no 
cork present, breaking through to form a blister-like spot. The oily outline is distinct, 
with only a faint yellow zone. Resembles infections on Fortunella margarita. 
Citrus mitis Blanco. Calamondin orange (CPB 11265 and 44305, seedlings), I, II, 
and II. 
A hardy tree, native to the Philippine Islands, and commonly grown in Hawaii. 
Some years ago distributed by nurserymen in this country under the name “tokum- 
quat.” 
The first two plants tested (15 inches) remained in a poor condition throughout the 
experiment, so that little or no Citrus-canker developed. However, the third plant 
(20 inches) has been in good condition for infection. Canker has been rather severe 
on the plant and has caused some defoliation of the leaves. Spots are present on the 
upper surface of the leaves. Not as susceptible as grapefruit. 
The spots (PI. 52, A) are many, small to medium size, light brown, and raised, 
compact, corky, forming a depressed dead area on the upper surface. Oily outline is 
indistinct, while yellow zone is scarcely visible. 
Citrus sp. "Naranja,” native orange (CPB 7929, seedling), II. 
A recent importation from Porto Rico. Leaf characters very much like a grapefruit. 
The plant (15 inches) has been in fairly good shape for infection and Citrus-canker has 
been severe. About as susceptible as grapefruit. 
. The spots (PI. 51, A) are fairly numerous, medium to large, light brown, raised 
spreading, corky, breaking through the upper surface to form a depressed dead area 
or a raised spreading spot. The oily outline is quite distinct, while the yellow zone 
is almost absent. 
Citrus sp. Kansu orange (CPB 11242, seedling), II. 
An interesting plant collected by Mr. Frank N. Meyer in North China and not yet 
described. Apparently very hardy. 
The plant (20 inches) thrived very well in the greenhouse, and new growth has been 
abundant. While Citrus-canker has developed on most of the mature leaves, it is 
causing no injury to the foliage whatever, and it gives promise of showing considerable 
resistance to canker in this respect. 
The spots (PI. 52, B) are many, extremely small (0.3 mm.), and not increasing in 
size, dark brown, raised, compact, not corky, not breaking through to upper surface. 
In fact, Citrus-canker can not be detected from a glance at the upper surface of the 
leaves. The oily outline is absent, and there is not the faintest trace of a yellow zone. 
Three species of Citrus known in the Philippines as “colo-colo” (CPB 7820), “talami- 
san” (Pi. 51, D) (CPB 7827), and “tegi-tegi” (CPB 7818) proved susceptible, resem¬ 
bling in type of infection, respectively, sweet lemon, grapefruit, and citron. 
