THE FUNGI WHICH CAUSE PLANT DISEASE 47 



It is closely related to but is not identical with B. solanisaprus 

 and B. atrosepticus.*^* 



B. populi Brizi is said to cause galls on the poplar ^^. 



B. pseudarabinus R. G. Sm."" is capable of producing on inocu- 

 lation a crimson-red gum in the vessels of sugar cane and is per- 

 haps responsible for a disease showing this symptom. 



B. rosarum Scalia is the name given to a very imperfectly 

 described organism said, on scant evidence, to be the cause of rose 

 tumors or crown galls.^* 



B. sesami Malk.*^ Malkoff in infection experiments caused a 

 disease of sesame with this organism. 



B. solanacearum E. F. Sm. (Group number 212.333-8—.) 

 A medium sized, easily stained, strictly aerobic bacillus with 

 rounded ends; about 1J^3 times longer than broad; 0.5 x 1.5 ai. 

 Motile, sluggish or active; flagella long, difluse. Spores not 

 known. Zooglcea occur in liquid media as small, white flecks or 

 as surface rings. It grows well at 20-30°. Milk is saponified with 

 no casein precipitation or acidity. Gelatine not liquefied. Agar 

 surface colonies, dirty-white. Agar streaks first dirty-white, later 

 yellowish to brownish-white, then brown. On potato as on agar, 

 but darker,' with substratum and fluid browned. No gas from 

 cane sugar, lactose, maltose or dextrose. 



The disease caused by this bacillus upon tomato and other 

 plants was early studied by Halsted "i'^^^ g^^ perhaps by Bur- 

 fjll 134-136 Halsted made inoculations which produced the disease 

 but he did not use pure cultures. The first complete account of 

 the causal organism was given by E. F. Smith "^' "' in 1896. 



In its hosts the bacillus is found in the pith, in the xylem which 

 is browned, and more rarely in the bark. From the cut ends of in- 

 fected ducts bacteria exude as a viscid ooze and the diseased ducts 

 may be traced to great distances through the plant, even from root 

 to leaf. From the bundles the organism later invades other tissues. 



Needle prick inoculations in tomatoes and potatoes with pure 

 cultures, were followed after several weeks (tomato) by typical 

 disease. Inoculations in Irish potato resulted similarly, though in 

 this host the parenchjona and bark were eventually invaded, and 

 the tuber was reached through its stem end and rotted. In South 

 CaroUna, Smith noted the disease on egg plants and crude cross 



