346 
Journal of Agricultural Research 
Vol. XIV, No. 9 
Citrus -aurantifolia (Auct.) Swingle (C. limetta Auct., not Risso.). Sour lime (CPB 
7338, seedling), II. 
The plant (18 inches) has been in fairly good shape for infection. Canker spots 
developed shortly after inoculation and have spread rapidly. At the present time 
the majority of the mature leaves are infected. While no defoliation has taken 
place, the plant is susceptible to a large degree. 
The spots (PI. 51, C) are numerous, small to medium size, rather dark brown, 
slightly raised, flattened on top, with some cork present. They break through the 
upper surface, forming either a small slightly raised spot or a depressed dead area. 
The oily outline is quite distinct. No yellow zone is present. The type of spot is 
rather characteristic and can not be compared directly to any of the other types 
discussed. 
Citrus grandis (L.) Osbeck (C. decumana L.)- Grapefruit (CPB 11170, seedlings), 
I, II. 
The plants (12 inches) have been in only fair condition, so that infection was not 
as heavy as might be expected of grapefruit. However, spots have developed on 
the leaves and twigs. Some defoliation has taken place. The plants are extremely 
. susceptible. 
The spots (PI. 50, B) are few per leaf, large (5-6 mm. in diameter), brown, raised, 
spreading, corky, breaking through the leaf and forming the same type of spot. The 
oily outline is very distinct and the yellow zone wide. A few spots on a leaf are 
sufficient to cause defoliation. The size of the spot is influenced somewhat by the 
number to the leaf. 
Citrus grandis (L.) Osbeck (C. decumana L.). Grapefruit (budded on Poncirus 
trifoliata, Alabama). 
As the plant (13 inches) was in poor shape for infection during the course of the 
experiment, only a few spots developed on the old leaves. However, they are typical 
of those on the preceding plants except in size. The degree of susceptibility of a 
plant can be judged somewhat by the number of spots occurring on the old tough 
foliage, as in the case of this plant. 
Citrus grandis (L.) Osbeck (Citrus decumana L.). Pummelo (CPB 7834, seedling), II, 
The leaf characters of this plant are very similar to grapefruit. However, the shape 
of the leaf differs somewhat, and the petiole is more winged. 
The plant (13 inches) has been in excellent shape for infection, owing to the rapid 
growth of the young foliage. Citrus-canker has developed on the leaves, also along 
the midrib on the upper surface, twigs, and thorns. The plant is extremely suscepti¬ 
ble, more so than grapefruit. Defoliation of the upper leaves by Citrus-canker has 
been rapid. 
The spots (PI. 51, B) are typical of those found on grapefruit in all details. 
Citrus grandis (B.) Osbeck. Hirado Buntan (?), Pummelo. (CPB 7993, seedling), 
II 
A plant very similar to the preceding form, except that the petiole is slightly more 
winged. 
As the plant (12 inches) made a rapid growth in the cases, Citrus-canker developed 
very early in the experiment. It is extremely susceptible, and defoliation by canker 
has been rapid. Apparently it is about as susceptible as pummelo 7834. 
The type of spots (PI. 50, B) produced is similar in all respects to those on grapefruit. 
The identity of this pummelo as Hirado Buntan is in doubt as the plant numbers 
became mixed in transferring them from the greenhouses in Washington. In Japan 
the Hirado Buntan was noted by Mr. Swingle in 1915 as being decidedly canker- 
resistant. 
