896 EXPERIMENT STATION RECORD. 



be the same disease in eggplants, and inoculations made upon vigor- 

 ous tomato shoots showed the probable identity of the disease on the 

 different plants. During the past year all the experiments of 1895 

 were repeated many times upon the tomato and potato, leaving no 

 doubt as to the existence of a bacterial disease, or as to the particular 

 organism to which it is to be attributed. The disease was repeatedly 

 produced from pure cultures, and the same organism has been reisolated 

 and a second series of successful inoculations instituted. The inves- 

 tigations are not considered complete, but they have advanced sufiici- 

 ently far to make it advisable to put on record what has been learned 

 concerning tlie parasite. 



The cause of the disease is a bacill'is, to which the name Bacilhis 

 solanacearum has been given, which is brietly characterized as follows: 

 A medium-sized bacillus, with rounded ends; often in pairs, with a 

 plain constriction; elliptical, varying in size with the age of the cul- 

 ture or length of time the tissues of the plants have been occupied; 

 usually 1^ to 3 times as long as broad. Cover-glass preparations 48 

 hours old stained with methyl violet show many specimens 1.5 by 0.5//. 

 The organism is but slightly motile, especially when taken from the 

 plant, but in young cultures sometimes becomes very actively so. The 

 Hagelhi are much longer than the rod, but the exact number and place 

 of attachment was not made out. No spores have been observed 

 either in the plant or culture media. Zoogloea are formed almost from 

 the start in the upper layers of the fluid culture media. 



The first prominent indication of the disease is the sudden wilting of 

 the foliage, which may occur first on a single shoot, but finally affects 

 the whole plant. Subsequently, if the plant is young and not very 

 woody, the stem shrivels, changing to a yellowish-green and finally to 

 brown or black. The vascular bundles become brown before the shriv- 

 eling takes place, and in the potato often show through the outer green 

 parts of the stem as long dark streaks. The vessels of such bundles 

 are filled with the bacilli, which ooze out when the stem is cut across. 

 If bacteria are abundant the wilt is often sudden, the foliage wilting 

 without the preliminary yellowing. TliQ progress of the disease seems 

 to be more rapid in young than in old jdants and in hot than cold 

 weather. In the case of the potato the tubers are finally attacked and 

 destroyed. A brown or a black rot ensues, beginning at the stem end 

 of the tuber in the vascular ring and extending in all directions. 



The anatomical changes in the host plant have not been worked out 

 fully, but it appears that the starch grains are uninjured by the organ- 

 ism, and lignified tissues are not affected by it. The organism attaclcs 

 the parenchyma of the pith and bark and also destroys the protoplasm, 

 converting nearly the whole interior of soft*stems into a nnissof broken- 

 down cells mingled with bacteria. In old and welllignified stems, like 

 those of well-grown tomatoes and eggplants, the outline of the stem is 

 better preserved and the lesions are less extensive. In the tubers of 



