MOSAIC OF SUGAR CAXE AND OTHER GRASSES. 17 
as it does from a common starting point, there is seen to be nothing 
to substantiate this claim. 
Only a few specific observations of infection may be cited in the 
limited space available. In October, 1918, healthy seed of about 80 
varieties was brought into the infested area from disease-free regions 
in order to determine whether any natural immunity existed among 
the varieties present in Porto Kico. This seed was planted at the 
Santa Kita estate, near Yauco. When the seed germinated, the 
young plants were seen to be healthy and normal, but within six 
weeks to two months practically every plant of all varieties with one 
exception (the Japanese Kavangire) showed the unmistakable symp- 
toms of mosaic. This was a clear case of secondary infection from 
the fields of diseased cane surrounding the test plat. 
At Santiago de las Vegas, Cuba, about 200 seed pieces of Java 228 
cane imported from Tucuman, Argentina, were planted in two rows, 
and two rows of the native Crystalina cane were planted beside them. 
The Java cane was 100 per cent infected when it came up, the cut- 
tings having come from diseased parent plants. When this planting 
was examined in June, 1919, 75 per cent of the Crystalina plants 
were characteristically diseased. The Crystalina seed pieces had 
come from a field which was minutely searched and found to be en- 
tirely free from disease. No other cases were found in the entire 
region, in fact, with the exception of a single stool of L 511 imported 
from Louisiana. 
In July, 1919, a field of D 74 stubble cane, grown for sirup near 
Cairo, Ga., was found to be healthy with the exception of one corner 
near the kitchen garden, where about 80 per cent of the plants had 
the mosaic. Investigation revealed the fact that a patch of green 
chewing cane had been growing adjacent to the D 74 at that corner 
during the preceding year. The green cane was found growing else- 
where on the farm this year, and examination showed that every 
plant had the mosaic disease. Clearly the D 74 had become infected 
last year, the disease had survived the winter in the stubble, and the 
shoots were diseased when they appeared again. 
At Washington, D. O, 17 varieties of cane, all diseased, are growing 
in an insect-proof quarantine greenhouse. 1 From time to time 
healthy sugar-cane plants in pots have been taken into the greenhouse 
and left exposed to the contagion. Invariably they show the incip- 
ient symptoms of the disease on the average in 17 days, proving that 
the incubation period is from two to three weeks. As has been men- 
tioned elsewhere, sorghum and wild grasses taken into this greenhouse 
have also become infected. Much more evidence of this kind could 
be adduced, but it is believed to be sufficiently clear that infection 
i Insects were present in the greenhouse. 
