64 A Bacterial Spot of Citrus 



Morphology. 



The organism is a rather slender rod with rounded ends ; the Uving 

 rods diffusing from discoloured cells in the rind of a lemon measured 

 •8 to 3-2 /A by -5 to -T/x; in a smear from the same source stained with 

 dilute fuchsin they measured 1-4 /x by -45 to -T/x, the majority in each 

 case were about 1-5 x -5 to -6 /x. Similar measurements were recorded 

 for rods from diseased tissues of spots on oranges and naartjes. The 

 l)acilli in the viscid mass oozing from affected fruit are shghtly stouter 

 on the whole than those in the tissues^ most of them are -6 to -65 /x in 

 thickness, in length there is not much variation. 



Measurements of rods from a 24 hour culture on nutrient agar and 

 in nutrient broth coincided with those of rods taken direct from the 

 tissues of the host plant, but on gelatine they are considerably shorter, 

 the majority measuring -8 to 1 /x by -5 to -G/x. In Uschinsky's solution 

 short forms also predominate. 



In old agar streaks the rods vary very much in length, some are 

 almost spherical, others attain a length of 5/x before dividing; some 

 stain intensely, others faintly or unevenly. 



No long filaments have been observed in the pellicle on sugar broth, 

 the longest unsegmented forms noticed in these media were about 8/x 

 in length. 



The sediment in three months old broth cultures consists for the 

 most part of rather short rods, some of which stain intensely with 

 gentian violet, but the majority stain faintly or unevenly. In old 

 cultures on steamed potato there are also a large number of individuals 

 which only stain faintly, and these are considerably swollen so as to 

 be elhpsoid or almost spherical in form. 



Fission. The multiplication of the organism by fission was studied 

 on the agar hanging block ; a smear was made from a 24 hour old 

 broth culture which had been incubated at a temperature of 35° C, 

 the preparation was illuminated by a Nernst lamp, and the lenses used 

 were a Zeiss jV" oil immersion objective and No. 12 compensating 

 ocular. With this magnification the alteration of the rods in size 

 and form could be easily followed, and drawings were made with the 

 camera lucida at frequent intervals. The temperature of the room 

 was approximately 26° C. 



At 9.15 a.m. a single rod was selected for study (Plate XII, a). 

 It at once elongated somewhat, became constricted and by 10 a.m. 

 had divided into subequal rods. The upper of the two new individuals 



