10 BULLETIN 14*74, IT. S. DEPARTMENT OP AGRICULTURE 
freely on the dead grapefruit twigs than on the orange. This latter 
condition would indicate that the grapefruit is subject to a heavier 
spore barrage than the orange, and the former would then have a 
greater mathematical chance to become infected. This alone might 
account for an appreciable amount of infection in excess of that 
occurring on the orange, but the results of inoculation experiments 
reported in Tables 3 and 4 indicate that the grapefruit is inher- 
ently more susceptible than the orange. 
Of the 21 hybrids under observation, all were found to be suscepti- 
ble to melanose. The disease has been observed on them in approxi- 
mately the following order: 
PRESENT 
Citradia (trifoliate orange and sour orange). 
Limelo (Rangpur lime and sour pummelo). 
Limelo (Mexican lime and sour grapef ruit ) . 
SLIGHT TO MEDIUM 
Rusk citrange (trifoliate orange and sweet orange). 
Citremon (Lisbon lemon and trifoliate orange). 
Natsumikan (probably pummelo and a kid-glove orange). 
Siamelo (King orange and grapefruit). 
Tangelos, Sampson and Thornton (tangerine and grapefruit). 
Tangor (tangerine and orange). 
SEVERE TO VERY SEVERE 
Thomasville citrangequat (Nagami kumquat and Willits citrange). 
Faustrime (Mexican lime and Australian finger lime). 
Faustrimedin (Australian finger lime and calamondin). 
Lemelo or lempum (Chinese pummelo and Myers lemon). 
Lemon hybrid (probably lemon and citron). 
Lemonime (Mexican lime and Genoa lemon). 
Lemonquat (Genoa lemon and Nagami kumquat). 
Limequat (Mexican lime and Marumi kumquat). 
Microcitrus hybrid (probably Australian finger lime and Fooji lime). 
Orangelo (grapefruit and orange). 
Tangelolo (grapefruit and Sampson tangelo). 
The kumquat hybrids are very readily blemished, more so than 
most grapefruits and at least as severely as the kumquats, but the 
tangelos as a class seem to be even less susceptible than the tangerine. 
GEOGRAPHIC DISTRIBUTION 
REPORTED OCCURRENCES 
Since there are several diseases that can easily be confused with 
citrus melanose, it is probable that some of the reports of the occur- 
rence of this disease in foreign countries, and even in America, may be 
erroneous. It is evident that the melanose of mandarins as reported 
by Trabut and the false melanose of sweet oranges in Australia as 
described by McAlpine are distinct from the American disease, and 
probably Lee in Japan mistook spray injury for melanose. 
Citrus melanose, therefore, seems to be confined to the Americas, 
including the West Indies. It has been reported from Brazil, the 
British West Indies, Porto Kico, Isle of Pines, Cuba, and Mexico, 
and in the United States in the States of Florida, Alabama, Missis- 
sippi, Louisiana, Texas, and California. 
