92 Disease of Frfflf Blossom 



Probably the start of an outbreak at the beginning of the flowering 

 season occurs in two ways. In the first place it seems likely that in 

 cases where blossom is produced on a spur the tissues of which are 

 already infected with the organism, some of these blossoms are infected 

 at the time of their formation through the spur tissues. In the second 

 place, since the organism has been found in the soil of fruit plantations, 

 it is likely that insects or wind convey infection from that quarter in 

 many cases. 



In the hght of present knowledge the organism seems to be a form of 

 very wide, if not general, distribution in this country, occurring at times 

 in the soil of fruit plantations and possibly having a natural habitat in the 

 soil. It is frequently found in flowers, especially such as rosaceous species, 

 where a prominent nectar-secreting disc, on which it appears to thrive, 

 is present ; becoming parasitic in some cases, notably the pear, perhaps 

 being aided in obtaining entry to the tissues through frost or other 

 damage. It is carried from flower to flower by bees ; and finally, in 

 the case of the pear at least, is capable of gaining access to the tissues of 

 the fruit spurs and remaining in an active state there throughout the year. 



Infection Experiments. 



These experiments have been mainly carried out on pear blossom, 

 flowers of the varieties Catillac, Beurre d'Amanlis, Louise Bonne de 

 Jersey, and Vicar of Winkfield being for the most part used. The 

 number of flowers infected was very large, and the infection was in 

 nearly all cases successful. 



The usual procedure in these experiments was to select young healthy 

 shoots bearing blossom in an unopened or comparatively unopened 

 condition, any individual flowers showing traces of natural infection 

 being removed. After infection the shoots were kept in the laboratory 

 or greenhouse at ordinary temperature in covered glass vessels, the 

 atmosphere of which was kept moist bv the water in which the cut 

 ends of the shoots were placed. The mode of infection varied. In some 

 cases drops of water containing the bacteria were simply placed upon 

 various parts of the flower by means of a sterilised ])latiiuim loop, care 

 being taken to avoid injury to the tissues of the flower. In other cases the 

 culture was applied with a fine needle, the tissues being slightly pricked. 

 It may be added that in all infection experiments pure cultures of the 

 organism were alone used, the usual precautions against foreign infection 

 being taken by the use of sterilised instruments and other necessary 



