S. G. Paine 65 



The causal organism is then B. carotovorus, a rod-shaped organism of 

 varying length motile by 3-6 peritrichous flagella. It stains well with 

 the usual stains and is Gram negative^. 



Host plants and distribution. The distribution of the disease seems to 

 be general throughout Great Britain and Ireland and a great variety of 

 hosts are liable to attack. B. carotovorus has been found by several in- 

 vestigators to be capable of producing rot in a great variety of plants, in 

 the roots of carrot, white turnip, parsnip, rape, radish, salsify, in onion 

 bulbs, hyacinth corms, cabbage, cauliflower, celery stalks and potato 

 tubers. No rot has been produced in young carrots or parsnips, apple, 

 pear, beetroot, sugar beet, swede turnips or tomato stems. 



Heart-rot of Celery. 



A soft rot of celery, in which sometimes the petioles of the outer leaves 

 only, but in more serious cases the heart and subsequently the whole 

 plant, are reduced to a yellowish brown decaying mass, was described by 

 AVormald in 1914(49) and an organism was isolated and named B. apio- 

 vorus. The disease had previously been observed in Ireland by Johnson 

 and Adams in 1910(19) who had isolated an organism but had not studied 

 it fully. In a later paper Wormald(50) gives the results of a comparison 

 of his organism with a strain of B. carotovorus, which we have had growing 

 in this laboratory since 1912 when it was obtained from America through 

 the courtesy of Dr E. F. Smith. As the result of this later work Wormald 

 concludes that the two organisms are identical and that "Heart-rot" of 

 celery is the work of that omnivorous organism B. carotovorus. 



"BLACKLEd" OF THE POTATO. 



This is a disease which produces entire destruction of the plant when 

 the attack occurs early in the season and a disastrous soft rot of the 

 tubers during storage when, following a late attack in the field, a certain 

 percentage of the tubers are so slightly affected at the time of lifting that 

 their diseased condition goes unnoticed. The rot spreads from these 

 diseased tubers to neighbouring healthy ones and the loss of the whole 

 or a considerable part of the store frequently results. 



1 In order to save space no attempt is made in this article to give the full description of 

 the cultural and physiological characters of the various organisms dealt with. These are 

 readily available in the literature and where a full description of an organism is given in 

 any paper to which reference is made an asterisk has been placed against the reference in 

 the list of literature cited. 



Ann. Biol, v 5 



