68 Bacterial Diseases of Plants 



an accompanyinn; brown stain rendering the vascular bundles clearly 

 discernible through the cortical tissue. The organisms enter the potato 

 tuber through the stolon and produce there a brown stain in the vascular 

 ring. From this the disease spreads as a brown rot into the storage tissue 

 which is finally completely destroyed. 



Massee(28) states that the disease has been recorded from several 

 districts in the North of England and in Scotland. He gives a drawing 

 which is strongly suggestive of Smith's disease and it is highly probable 

 that the disease exists in this country, though in the absence of any 

 evidence of the isolation of the causal organism it is still uncertain 

 whether the English disease is etiologically identical with the American. 



Iris Rot. 



The leaves become yellow, wilt and die. The underground portion 

 of the plant becomes completely rotted. Massee(29) states that the disease 

 is quite common in this country and the author has seen it in the beds at 

 the Chelsea Physic Garden though the causal organism has not been 

 isolated in this country, van Hall(i5) found B. omnivorus and two species 

 of Pseudomonas responsible for the disease on the continent. 



Yellow Disease of Hyacinth. 



Wakker's Disease of Hyacinth due to P. Hyacinthi and fully de 

 scribed by Smith (42) occurs in our nurseries but, so far, not to any great 

 extent. The organism was isolated by the writer from a diseased corm, 

 recently imported from Holland, growing in one of our large nurseries in 

 1915 and was found to give all the characteristic reactions of P. 

 Hijacinthi and to give rise to the characteristic symptoms of the disease 

 in a corm of Koman Hyacinth {Hyacinthus orientalis) when the cut 

 surface of this was smeared with a loopful of the organism from an agar 

 slope. 



Black Rot of Cabbage and other Cruciferous Plants. 



The bacteria enter the leaf through the water pores causing a yellow- 

 ing of the neighbouring tissue. They pass then to the veins, which become 

 strongly blackened, and travel by way of the vascular bundles to the 

 root which may become almost entirely hollowed out by the rot. The 

 disease is also spread by slugs and this is probably the more usual method 

 of infection. 



