348 
Journal of Agricultural Research 
Vol. XIV, No. 9 
Citrus excelsa Wester (CPB 11280, seedling), II. 
A citron-like plant recently introduced from the Orient. 
Owing to the poor condition of the plant (10 inches), little Citrus-canker has devel¬ 
oped. However, what few spots are present on the leaves resemble those on the 
citrons. 
These results obtained show that all of the Citrus fruits are more or 
less susceptible to Citrus-canker. While it is true that the plants 
included in the inoculation experiments represent only a small portion 
of the species and varieties found in this group, apparently the only 
plants which show any marked resistance to Citrus-canker are those 
included under Citrus nobilis and the Kansu orange. Citrus mitis, 
which has been reported to be resistant to canker in the Philippines ( 26 ), 
can hardly be classed with the promising resistant forms under green¬ 
house conditions. However, tests with this species will be repeated 
both in the greenhouse and in the field. 
The type of spots produced on the various plants are striking, and in 
many cases the plants can be classed from a botanical standpoint, and 
relationships traced by the character of the spot. The susceptibility of 
the plants can also be arranged by the number and type of the spots 
per leaf. The spots vary from 6 mm. in diameter on grapefruit (PI. 50, 
B) to 0.3 mm. on the Kansu orange (PI. s 2 , B). While the size of the 
spot is influenced to some extent by the number of spots on the leaf 
surface, apparently those plants on which the small spots are found are 
not as susceptible as those with the large spots, as in the case of grape 
fruit. 
SUSCEPTIBILITY OF CITRUS HYBRIDS 
Faustrime (C. aurantifolia , West Indian lime, X Microcitrus australasica) (CPB 
49819 and 49823, cuttings), II. 
These hybrids retain to a large extent the characteristics of species of Microcitrus. 
The plants (12 to 18 inches) have not been in good shape for infection during the 
experiment. Not much new growth has developed, so that they have not had a 
good test. 
Up to March 1, 1918, only two small spots (PL 53, F) have developed, one at a 
puncture and the second on a small leaf. Microcitrus australasica has remained 
resistant, so that it is interesting to note that the hybrid is very slightly susceptible. 
Faustrimon (C. Limonia , lemon, X Microcitrus australasica). (CPB 49824 and 49843, 
cuttings), II. 
The plants (6 to 8 inches) are smaller and resemble very closely Microcitrus austra¬ 
lasica. The growth of the foliage has been very slow so that they have been in only 
fair shape for infection. 
No spots of any kind have developed on the leaves. 
Citrange, Colman {Poncirus trifoliata X C. sinensis). (CPB 7896, seedlings), I, II. 
The plants (18 inches) have been in only fair shape for infection. However, Citrus- 
canker appeared shortly after the first inoculation (15 days) and spread quite rapidly 
over the mature leaves. During the colder weather, when it was impossible to main¬ 
tain a high temperature, the plants defoliated quite badly, so that few infections have 
occurred during the last two months. This was true of all the citranges. 
