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Detection of very mild strains of virus has been enhanced by the use of a modified U.C. soil mix (3) to produce maximum plant growth free from patterns of nutrient deficiency or excess, and by supplemental lighting during the winter months (4).Investigations on indicators for concave-gum virus revealed that the Dweet tangor [Citrus reticulatu Blanco x C. sinensis (L.) Osb.] is a very efficient indicator for a mild strain of the virus and is also sensitive to psorosis-A and crinkly-leaf viruses (4). Despite a mild spotting that may appear on uninoculated seedlings, the superior sensitivity of Dweet tangor to psorosis-type viruses makes it a desirable indicator plant. After 1963, all new candidates entering the Variety Improvement Program were indexed on Dweet tangor, and over 150 candidates not previously indexed on Dweet were tested. One result of this re-indexing was detection of a psorosis-like mottle (Fig. l,A) on leaves of the Dweet indicator inoculated from a Cleopatra mandarin (C. reticulata Blanco) (CRC 270 in 8A-13-50). The parent tree showed no visible evidence of damage or decline due to virus infection, although the fruits were small, the twigs

THIS PAPER is concerned with a severe disease of natsudaidainext to satsuma, one of the most important varieties of citrus in Ehime Prefecture. Growers have given it the name "ishidama-mikan," meaning stonelike fruit, because fruit on affected trees are depressed in growth after the June drop and their rind surface becomes abnormally smooth, lustrous, and hard (Fig. 1'). The small

The plague suppressive campaign which is now drawing to a close in San Francisco has been conducted almost entirely on the principle that the great factor in the spread and continuance of the disease is the rat. The fact that the epidemic among human beings ceased within four months after the beginning of active operations and that in spite of the distribution of the disease in almost every quarter of the city, only one hundred and fifty-nine cases, with seventy-seven deaths occurred, proves the wisdom of this policy. The campaign has been conducted by the United States Public Health and Marine Hospital Service.