12 



During this time, the leaflets of the same leaf which were punc- 

 tured but not inoculated remain healthy, and it is nine or ten days, 

 on the average, befoie the disease reaches them. In a few days more, 

 these leaflets also are dead. The disease now travels down the main 

 leaf stalk and enters the stem, where it progresses slowly from node 

 to node, killing the leaves and finally it may kill the whole plant. 



All inoculated plants developed the characteristic symptoms of 

 the disease, and all were, at some period, examined for bacteria. The 

 characteristic bacteria were found in every instance, and in aW parts 

 examined which showed the symptoms. Numerous check plants, kept 

 under the same conditions, but not inoculated, showed no symptoms 

 of the disease, but remained healthy and, on examination, no bacteria 

 could be found in their tissues. Plate cultures from the diseased 

 tissues ot" inoculated plants developed uniform pure cultures of the 

 germ inoculated into them. Sections of the inoculated j)lants showed 

 characteristic bacteria present within the cells and especially numer- 

 ous within the woody bundles ; the vessels being choked with them 

 and the cell walls frequently dissolved. 



Prevention. 



No remedy is known for the disease after the symptoms once 

 appear in the plant. Measures may be suggested, however, to prevent 

 ite introduction and spread. Seed containing the bacteria must not 

 be planted. Such seed may be much discolored, may show slight 

 evidence of infection, and for this reason seeds from fields where the 

 bean plants have shown symptoms of the (disease should not be 

 planted, even though such seed has been carefully picked over and 

 all discolored beans removed from it. This precaution in the selection 

 of healthy seeds applies wifeh special force to the planting of new fields 

 where beans have not been grown. It is hoped that a method of 

 treating the seed may be worked out, by which the bacteria may be 

 surely killed without injury to the seed. This germ, Fseudonionas 

 phaseoli, forms no spores and is readily killed in water heated to only 

 122° F., for ten minutes, a temperature which dry bean seed can 

 endure for some time without injury. It is readily killed, also, by a 

 solution of mercuric chloride, one part to 1,000 of water. 



A field where beans have sickened with this disease is unfit for 

 growing beans for at least one season, as the germs live over at least 

 one winter in the stems and leaves left on the ground. How long 

 such a field may remain infected is unknown, for we do not yet know 



