342 Mycologia 



dissemination in the cane regions remains to be proved. The 

 failure of the sharp-headed grain leaf-hopper to transmit the dis- 

 ease under the conditions of these experiments is surprising. 

 This insect is very common on cane in Louisiana, and as a result 

 of field observations suspicion was directed toward it from the 

 first. Other leaf-hoppers are now being tested. The successful 

 experiments with the corn aphis are of great interest scientifically, 

 but it is believed that transmission of mosaic is restricted to this 

 insect or to other aphids more abundant on cane. Aphis maidis, 

 however, has been reported on sugar cane from practically every 

 sugar-cane region in the world. That cane mosaic is analogous 

 with other mosaic diseases is brought out by a number of facts, 

 aside from the visible signs of the disease. As in many other 

 mosaics, the infectious material does not seem to be highly spe- 

 cialized, but may attack other plants of the same family. The 

 cell sap of infected plants contains some organism, not visible by 

 ordinary means, which is capable of inducing the disease when 

 injected into healthy plants. Leaves which are mature at the 

 time of inoculation never show any signs of mosaic. This fact, 

 typical of all mosaics, has been brought out in all inoculation ex- 

 periments with sugar-cane. The disease can be transmitted by 

 certain sucking insects. There is no known period of sapro- 

 genesis in the existence of the virus. Seed transmission of the 

 virus is one of the phenomena concerning which divergent re- 

 sults have been recorded for the various mosaic diseases. This 

 point has not been definitely settled for sugar-cane mosaic, but 

 mosaic sorghum plants failed to produce mosaic progeny in two 

 experiments. 



