48 



THE FUNGI WHICH CAUSE PLANT DISEASE 



inoculations were made to tomato. Smith demonstrated experi- 

 mentally the efficiency of the potato beetle in transmitting the 

 disease. 



The disease was described for tobacco by Stevens ^^ and Stevens 

 and Sackett."^ 



Successful inoculations were reported upon tobacco by E. F. 

 Smith in 1909 ^^^ though in his eariier trials tobacco and pepper 

 gave negative results when inoculated with this bacillus. In addi- 

 tion to the above hosts it is known to grow upon Datura, Solanum 

 nigrum, Phj^salis and Petunia. 



B. solanicola Del. was reported as the cause of a potato stem 

 disease. ^''^ 



B. solaniperda Mig. (Group number 121. 0--.) A rod, 



2.5-4 X 0.7-0.8 M, with rounded ends, often in long chains; actively 

 motile ; spores present. Agar colonies dirty- white ; gelatine liquefied. 

 This was shomi by Kramer in 1890 ^^^ to be the cause of soft rot 



of potatoes. The organism 

 was grown in pure culture 

 and inoculated on potatoes 

 producing the characteris- 

 tic decay. The germs enter 

 through the lenticels, con- 

 sume the sugar, then at- 

 tack the intercellular sub- 

 stances and the cell wall. 

 Later the albuminous sub- 

 stances are destroyed. 



B. solanisaprus Harr. 

 (Group number 221.212-0- 



_ \ 143 



A bacillus with rounded 

 ends, 1.5-4 x 0.6-0.9 m, 

 variable in culture; no capsule; actively motile by 5-15-1- peritri- 

 chiateflagella; no spores seen. Gram negative. Gelatine colonies, 

 punctiform 0.25 mm. at two days ; gelatine stab filiform. Liquefac- 

 tion noticeable on the thirty-fifth day. Agar colonies punctiform 

 at two days, 1-5 mm., gray-white, slimy, flat. Bouillon turbid 

 with fine sediment; ring, and thin band present; milk curdled. 



Fig. 31.- 



-Surface colonics of B. solanisaprus. 

 After Harrison. 



