A. F. Blakeslee 27 



Most of the species tested seem immune to the infection and unable 

 to transmit the virus. The Petunia is a typical example. In addition 

 to controls, eight attempts were made to infect this species by grafting 

 with Q. Jimson Weeds, but without success. In one case, shown in 

 PL VI, fig. 11, a Petunia cion was grafted on a Q. Jimson stock (Q.). 

 A month later a cion from a normal Jimson (N.) was grafted on to the 

 Petunia, leaving a distance of 16 cm. between the two grafts. Five and 

 a half months after the last graft was made the Jimson cion at the top 

 of the plant was still normal in appearance, and had produced two 

 spiny capsules while the original stock was still Quercina. Twenty-six 

 seeds from the second of these capsules were planted and produced 

 20 seedlings, all normal. It may be concluded that the Petunia neither 

 acquires the disease, nor is able to transmit the virus through as much 

 as 16 cm. of its stem. 



An experiment siruilar to that just described for the Petunia was 

 tried with the tomato. The virus failed to pass through 3*5 cm. of the 

 tomato stem and infect a normal Jimson graft above it. It is possible 

 that with a shorter distance the experiment would have succeeded, 

 since, in one out of three trials, a cion taken from a graft on a Q. plant 

 gave the disease to a normal Jimson when grafted on it. In this case, 

 however, the cion was cut off from very near the junction between the 

 tomato and the Q. stock, and it is barely possible that some of the tissue 

 of the latter was the cause of the infection. 



Both the two cions of Jerusalem cherry grafted on Q. stock produced 

 normal flowers with pollen and fruit, but their leaves, although normal 

 in shape and otherwise like the controls, were more or less blotched with 

 yellowish patches. Of two grafts from these infected cions on to normal 

 Jimsons, one transmitted the disease and the other did not. 



The egg-plant gave some evidence of being susceptible to infection. 

 Two cions were grafted on to Q. Jimsons. One grew but slightly and 

 hence had little opportunity to show the disease. The other cion pro- 

 duced a vigorous growth, with many flowers with pollen and finally 

 fruited. The leaves were normal in shape, but were puckered in a manner 

 shown by the earlier stage of infection in Datura meteloides. 



The only instance not already mentioned where a species showed 

 any evidence of being susceptible to Q. infection through grafting was 

 with D. Geratocaula. Of two cions grafted on to Q. Jimson stock, one 

 produced a flower without pollen and also two slightly abnormal buds 

 which fell off before opening. These latter buds had their corollas 

 more or less slit. Later flowers from this plant, however, were normal. 



