THE BEAN BLIGHT: TRANSMISSION 297 



can live over winter on naturally infected seeds (kept 

 both in the pods and in sterile test tubes) and also determined 

 that such seeds were not injured beyond the power to germinate 

 and grow, but does not state that he traced the disease on into 

 the seedlings derived from such seeds. 



It has not yet been proved experimentally that this disease 

 is commonly carried on the seed, unless we may assume that 

 Edgerton has done so, but such I believe to be the case (read 

 what is said under Nos. II and III, and respecting Rathay's 

 Disease of Orchard Grass in "Bacteria in Relation to Plant 

 Diseases," Vol. Ill, p. 160, and make all the observations and 

 experiments you can). My reasons for this belief in addition to 

 Barlow's statement, and Edgerton's, are the facts drawn from 

 my own observations that the bean bacterium is not very 

 sensitive to dry air, and that it may pass entirely through the 

 walls of the pericarp and infect the seeds without destroying 

 them, i.e., as they are approaching maturity. Such seeds, 

 which are usually more or less distorted, should be saved in 

 large numbers in sterile tubes and tested from time to time 

 through the autumn, winter, and spring, to determine: (1) 

 whether Bacterium phaseoli can be cultivated from many of 

 them; and (2) especially whether seedlings grown from such 

 seeds (in autoclaved soil and watered with boiled water) do 

 commonly become infected. 



Here is a definite, interesting, practical problem, easy of 

 solution — given a bean field containing an abundance of the 

 disease and a student with some aptitude for research. Five 

 hundred or a thousand diseased bean pods would not be too 

 many to save for such an experiment. A httle preliminary 

 observation will determine what pods should be selected, i.e., 

 how badly diseased they must be externally to warrant belief 

 that the pericarp has been perforated. Bean cotyledons are 

 often distorted and bear rusty spots when they emerge from the 

 soil. Is any part of this phenomenon the disease in question, 

 or is it all due to fungous infection? 



If Barlow's conclusions can be generalized, as seems prob- 

 able, we shall have a very simple and practical way of dealing 

 with this disease. 



