74 



On the motion of Dr. Howe, the appointment of the club's two 

 representatives in the council of the Association and the method 

 of their appointment in the future was left to a committee formed 

 of the officers of the Club. 



The scientific part of the program consisted of an illustrated 

 talk by Dr. L. O. Kunkel, of the Boyce Thompson Institute, 

 entitled "Virus Diseases." 



The virus diseases of plants as a group are transmitted by 

 insects. This is not known to be true of the virus diseases of 

 animals. Not only are we ignorant of the cause of these diseases : 

 we do not know what observations and experiments are neces- 

 sary in order to solve the problem of their etiology. 



There seems to be a specific relation between virus diseases 

 and the insects which spread them. Only certain insects are 

 able to transmit certain virus diseases. 



Dr. Kunkel described the symptoms of Aster Yellows, the 

 insect transmitting it {Cicadula sexnotata) , and methods of study, 

 illustrating his remarks by lantern slides. 



Slides were shown of the same disease on lettuce. Ambrosia 

 trifida, Asclepias nivea, Oyster Plant, Dandelion, Butterweed 

 (Erigeron canadense) , Sonchus sp., Paris Daisy, {Chrysanthemum 

 frutescens), Amaranthus auroro, Gypsophila, French Marigold, 

 Helichrysum arenarium, African Marigold, Mignonette, Schi- 

 zanthus. Dill, Anise, etc. 



In all cases the transmission of the disease was carried out by 

 the same insect. It cannot transmit the disease immediately 

 after feeding. An interval of at least lo days must elapse before 

 it becomes inoculative. This seems to be evidence that the 

 causal agent is a living organism, and not a purely chemical 

 substance. A certain incubation period exists here just as in 

 the case of the malarial parasite which passes an incubation 

 period in the body of the mosquito. 



It has been suggested that the virus diseases are due to ultra- 

 microscopic organisms. The virus diseases are very important 

 because they attack so many economic plants and also because 

 they are apparently closely related to certain diseases of animals 

 and human beings; e. g., rabies, foot-and-mouth disease, hog 

 cholera, small pox, typhus fever, etc. It is believed that the 

 discovery of the cause of virus diseases in plants would throw 

 light on the virus diseases of animals. 



