128 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



and even trained observers, in the employment of the terms " rot " 

 and "blight" as applied to diseases of the potato; and it is therefore 

 necessary to insist upon the distinction between the disease produced by 

 the fungus Phytophthofa infestans, termed " blight," and the soft or 

 wet "rot" caused by bacteria of several different species. The inability 

 to distinguish between the different types of disease gives rise to error 

 in combating them, and renders remedial measures frequently ineffective 

 because applied under a misconception as to the nature of the disease 

 under treatment. For instance, the Bordeaux mixture has been used 

 in the treatment of bacterial rot, to which it was manifestly inapplicable, 

 as the bacteria, being confined to the interior tissues of the stem and 

 tubers, could not be affected by external spraying. 



This bacterial rot of potatoes is distributed widely in Canada and 

 the United States, in Great Britain and other European countries. 



In the majority of cases the first symptoms of the disease appear 

 when the plants are in full vigour. The leaves droop and become 

 discoloured, while the stems lose their erect appearance and gradually 

 sink to the ground. Black areas are to be noted on the attacked stems 

 and leaves and sections, though these spots show the vascular bundles 

 brown or black according to the progress of the disease. In the tubers 

 this disease first appears as a reddish-brown discoloration of the skin 

 and subjacent tissues ; these at first are firm, but afterwards they become 

 soft, and there is frequently a black line of demarcation between the 

 healthy and diseased portions. As the rot progresses the flesh softens to 

 a white watery pulp with a highly offensive odour, and in the final stage 

 the potato becomes a mere mass of black pulp. 



The author considers that the natural infection is chiefly to be 

 attributed to the diseased condition of the seed potato, but the possibility 

 of the parasite maintaining its existence in the soil and entering a 

 healthy tuber through a wound is also admitted. The progress of the 

 disease is materially influenced by the amount of moisture in the 

 soil, and a large rainfall, followed by warm weather, presents the most 

 favourable conditions for the spread of the epidemic. 



Cultivations have been made of the Bacillus, and artificial inoculations 

 have shown that the following plants are liable to attack : — Jerusalem 

 artichoke, cucumber, carrot, radish, parsnip, cauliflower, cabbage, celery, 

 swede, turnip, mangelwurzel, salsify, tomato, and onion. 



The parasite is a Bacillus with slightly rounded ends, varying from 

 1*5 to 4 fjt by '6 to *9 /u. It is actively motile with a varying number of 

 flagella.-If. C. P. 



Bag Method of Keeping* Grapes. By J. Balsacq (Le Jardi?i, 

 vol. xx. No. 473, p. 324 ; November 5, 1906). — Another general article 

 on the advantages of this method. Suggests the advisability of experi- 

 menting with blue bags, on the lines of M. Flammarion's conclusions 

 as to the influence of coloured light on ripening of fruits. — F. A. W 



Bag* Method of Keeping" Grapes. By F. Charmeux {Le Jardin, 

 vol. xx. No. 4G5, p. 204 ; with 3 figs. ; July 5, 1906).— Under favourable 

 conditions (absence of birds, wasps, &c.) the bags now recommended at 



