o() Bacterial Blhjkt of Pear Blossoms in South Africa 



of blossom eventually dies and the spur may also die back to its point 

 of attachment to the branch carrying it. In other cases infection takes 

 place through the receptacle, which becomes blackened, the discoloration 

 spreading to the ovary. 



The disease is carried from flower to flower by bees. An organism 

 has been isolated and the disease repi'oduced repeatedly by Barker and 

 Grove in the course of their study of the disease ; and I was successful 

 in producing black spots on the receptacle with the culture which they 

 sent to me ; these latter developed rather slowly as the room tempera- 

 ture was far above the optimum for the organism. 



In a recent report (2) it is stated that an organism has been isolated 

 from diseased gooseberry bushes which is in all probability identical 

 with the organism causing the pear blossom blight. 



The Organism. 



A parallel series of cultures of this and the South. African organism 

 have been carried out; the characters of Barker and Grove's organism 

 are described in some detail in their paper (i) but a few additional points 

 of interest have been observed in making the comparative study, which 

 may be added to their description. 



Morphology. 



The organism is a rod 2 — 4 x -5 — -S/x,, the cells are mostly single 

 or in pairs, seldom in long chains. It is highly motile in young cultures 

 by 2 — 5, lophotrichic flagella (Fig. 1) which are four to five times as 



Fig. 1. Barker and Grove's organism 24 hrs. at 20° C. Ellis' Hagella stain, Zeiss 

 obj. j'.j , No. 12 compensating ocular. Drawn with the aid of the camera lucida. 



