SUMMARY. 43 



be detected, even in the dorniiint state, l)y examinin*;- for discolored 

 spots, but it is safer to start the plants in pots, even after the corms 

 having- discolored areas have been rejected, to insure getting- as few 

 diseased phmts as possible in the l)ed, since experience shows that souic 

 conns are so slightly afl'ected that the disease is not easily detected in 

 the dormant state. Some growers })refer to keep their j)lant3 in pots 

 throughout the season as a preventive measure against tiie rot, but as 

 a rule callas grown in this manner do not produce as hirge flowers as 

 when grown in a solid bed. Hence, if the tracU* demands a large 

 flower, the solid bed is preferable. 



In conclusion, the writer wishes to express his acknowledgment to 

 Dr. Erwiii F. Smith, pathologist in charge of the laboratory of phint 

 pathology, for his many helpful suggestions and his assistance in 

 carrying on this work, and also to jVIr. Alexander B. Garden, of Ana- 

 costia, D. C, for his kindness in allowing free access to his calla house 

 during the past four j^ears. 



SUMMARY. 



(1) The soft rot of the calla is a bacterial disease, 



(2) The organism that ]>r<)duces the calla rot is a short rod bearing 

 peritrichiate tlagella. 



(3) The orgaiiism occupies the intercellular sj^acc^ in its host and 

 dissolves the layers that coimect the cells, causing the afl'ected tissue 

 to break down into a soft, slimy mass. 



(4) The organism is able to attack a large number of raw vegeta- 

 bles, and is capable of producing soft rot in many of our useful plants. 

 Care should therefore be taken not to throw any deca3'ed or partl}^ 

 deca3^ed callas or the soil from a bed in wliich callas have decayed in 

 any place where the vegetables mentioned in this bulletin are to be 

 grown. 



(5) It does not attack tree fruits readily, and hence is not likely to 

 produce fruit rots. 



(6) It grows readily on beef agar, forming at room temperature (18"^ 

 to 25° C.) radiating colonies, while on the same medium at extreme 

 temperatures (8-' or 37°) the colonies are usually round. 



(7) It liquefies gelatin. 



(8) It coagulates milk, and first reddens, then ))leaches blue litmus 

 milk. 



(9) A 1-mm. loop of a fresh fluid culture of the organism placed in 

 10 c. c. of beef broth will distinctly cloud it in four hours at 35° C. 



(10) The organism does not produce gas when grown in a peptone 

 solution containing 1 per cent of cane sugar, milk sugar, glycerin, 

 maltose, dextrose, or mannite. 



(11) It bleaches litmus lactose agar. 



