662 
Philippine JouiMal of Science 
1919 
longitudinally with the branch; the last condition seems typical 
of the effect of Corticium. 
On Citrns the outermost layers of the wood become discolored 
to a light brown. The extent of this brown tissue, however, 
is small in comparison with the area covered by the surface 
mycelium of the fungus, and the discoloration of tissue has 
never been observed to extend deep into the wood. Brooks 
and Sharpies, in their study of the disease on rubber, found 
that the fungus hyphae followed the medullary rays well into 
the tissue. 
The ultimate effect of the growth of the fungus is the stop- 
page of the water conduction, followed by the wilting of the 
leaves and the ultimate death of the affected limb. This last 
stage takes place very rapidly; frequently the leaves wilt, 
yellow, and drop within a period of five days. Small twigs, 
main branches, or even trunks of trees are attacked (Plate VI, 
fig. 1, Plate VII, fig. 2) . It has never been observed on roots. 
The susceptibility of young and old trees seems to be equally 
great. The accompanying photographs probably show these 
stages much more clearly than can a written description. 
Pink disease has been found upon the following horticultural 
varieties of Citrus species: 
Citrus nobilis Lour.: Tizon, Kishiu, Suntara Nagpur. 
Citrus sinensis Osbeck: Native cajel. Pineapple orange, Washington 
navel, Mediterranean, Valencia, White Siletta, Jaffa, St. Michael, 
Sawyer’s navel, Navelencia. 
Citrus aurantifolia Swingle: Tahiti, West Indian, Dayap. 
Citrus limonia Osbe'ck; Valencia, Clark, Villa Franca, Messina, Belair, 
Lisbon. 
Citrus aurantium Linn.: Seville. 
Citrus maxima Merr. (C. decumana Linn.) : Marsh, Triumph. 
Citrus medica Linn. var. sarcodactylis. 
Citrus hystrix DC. 
Citrus micrantha Wester. 
Citmis 'wehberi Wester var. montana Wester. 
Citrus species: Natsumikan. 
Citrus hybrid: Tangelo, Sampson. 
Feronia elephantum Corr. and Murraya exotica Linn., the 
genera of which are closely related to Citrus, have also been 
observed as hosts of Corticium salmonicolor B. & Br. in the 
Philippines. The omnivorous character of the fungus and the 
diversity of Citrus varieties attacked by Corticium seem to in- 
dicate that the occurrence of species or varieties of Citrus re- 
sistant to the disease is highly im'probable. 
