228 



BACTERIA IN RELATION TO PLANT DISEASES. 



he has seen. Whether the Fusarium alone is sufficient to cause a wilt disease of tobacco 

 remains to be determined by experiment. Delacroix has recently described a Fusarium 

 disease of tobacco, and it is not improbable that two diseases may have been confused. 



With these facts in mind, the 

 writer suggested to Dr. McKenney 

 in the summer of 1912 that he visit 

 the tobacco fields of North Caro- 

 lina. This he did, but could then 

 find only the bacterial disease. I 

 still think, however, that a Fusarium 

 disease of tobacco will be found, 

 for, as I pointed out in 1899, this 

 widely disseminated form-genus 

 contains active parasites destruct- 

 ive to a great variety of cultivated 

 plants, a fact now generally recog- 

 nized, but then unknown to science 

 (Scientific American Supplement, 

 No. 1246, page 19981). 



The preceding statements rep- 

 resent the writer's knowledge of this 

 subject up to the summer of 1905, 

 if we exclude Uyeda's first paper, to 

 be treated a little later. That sum- 

 mer diseased tobacco plants were 

 sent to him from Quincy, Florida, 

 and from Creedmoor, North Caro- 

 lina. In both cases the cause of the 

 disease appeared to be bacterial, 

 and the signs of the disease corre- 

 sponded quite closely to descriptions 

 of the slime disease as it occurs in 

 Sumatra, and also to the signs men- 

 tioned by Stevens and Sackett. 



From the North Carolina ma- 

 terial agar poured plates were made 

 a number of times, and always large 

 numbers of one organism were ob- 

 tained from the inner tissues (pi. 37). 

 This was a short, motile bacterium, 

 the small roundish surface colonies 

 being gray-white at first on agar, 

 but afterwards brownish (pi. 23, 

 fig. 2). Usually the plates showed 

 no other organism present, but occa- 

 sionally scattering colonies of other 

 bacteria appeared. They were 

 made, of course, from clean parts 



Fig. 1l7.f 



*Fic. 1 1 6. Cross-section of petiole of a tobacco leaf, showing bacterial invasion of vascular system. From a natural 

 infection in North Carolina. Material for sections received in alcohol from Prof. F. L. Stevens. Slide 291 a 6. 



fPio. 117. Cross-section of a tobacco stem diseased by Bacterium solanacearum. A detail from slide 291 a 15, 

 section X, '. ., from the same source as fig. 1 16. A somewhat diagrammatic wash drawing. 



