28 Graft-Infectious Disease of Datura 



Except for the abnormalities of these three flowers in a single plant the 

 cions were normal in appearance. 



In Table VIII are listed the species tested by grafting with Q. 

 Jimson stock. Controls on normal Jimsons were tried in all cases. 



At least one other mosaic-like disease has been found infecting 

 Jimson Weeds. This has been called " Z." It was first noticed in two 

 adjacent plants in the field cultures of 1917. PL VI, fig. 12 is a photo- 

 graph of an infected individual. Infected plants are obviously diseased. 

 The leaves are light in colour, mottled, more or less eroded, and strongly 

 puckered resembling somewhat the badly diseased leaves of beans 

 attacked by mosaic. The leaves may be reduced to merely the midribs. 

 The capsules are deformed, with spines reduced or entirely absent. The 

 buds are generally elongated, the flowers " confused " with corollas 

 often split or otherwise malformed and with numerous accessory carpels 

 frequently developed. Infection develops rapidly in the plant and soon 

 renders it valueless for records or for the production of seeds. The disease 

 was first serious in the field cultures of 1919. From its spread from 

 centres of infection it was obviously transmitted by means of contact. 

 Attempts to communicate the disease to normal plants by rubbing them 

 with infected leaves were successful with some exceptions. No extensive 

 experiments have been made with this disease to discover what other 

 Solanaceous species are susceptible. It has not yet been found possible, 

 however, to transmit it to the tobacco {Nicotiana Tahacum) either by 

 rubbing the leaves together or by grafting. 



From smooth capsules of a Z plant 89 seeds were sown and gave 

 77 seedlings which remained normal. The experiments indicate that 

 the Z disease is infectious by contact of leaves but is not carried by 

 seed. 



VI. Early Records of Quercinas. 



It has not seemed profitable to search all the early records for de- 

 scriptions that would indicate plants with Q. infection. Naudin(7) 

 and Godron (6), as well as Bateson and Saunders (2), undoubtedly had 

 them under observation. It may be stated that the writer has grown 

 many thousand plants of the Jimson Weed, including large numbers of 

 individuals that were heterozygous for inermis capsules, but has never 

 observed any except Q.'s which showed a mosaic arrangement of the 

 spines on the fruits, with some valves smooth and others more or less 

 spiny. 



