158 Journal of AtjHculUire, Victoria. [10 March, 1916. 



prepare the way for the further advance of the bacteria. In the early 

 infections, if climatic conditions are favorable, lesions, or dark spots, are 

 formed, which often extend through the hull and shell-forming tissues 

 into the kernel. The nut in such cases is deformed in shape as the 

 diseased part ceases to grow. Such nuts do not bark clean, as the outer 

 covering clings very tightly to the shell, and the kernel at best is only 

 poorly developed. 



Late Infections.— Ti often happens that during the summer months 

 weather conditions are favorable for natural infection of nuts. At thii^ 

 time the outer tissue is beginning to harden, and is not in condition for 

 the deep growth of the disease that occurs earlier in the season, when 

 the tissue is more tender. The parts of infection appear as small, dark- 

 coloured areas scattered over the surface of the nut. Each little infec- 

 tion can be distinctly seen, or its confluence with others may make a 

 large spot. In these late infections the development is shallow, and 

 does not penetrate much through the epidermis, and the disease seems to 

 dry out and die. Occasionally a more severe late infection occurs, 

 where the blackening and lesion extend to the hard shell, causing the 

 hull to cling to the shell of the nut. 



White Deposit on Diseased Tissue. — On the surface of the diseased 

 tissue of both the branches and the nuts can often be observed a whitish 

 substance that accumulates during the summer, but at length disappears. 

 When this is properly stained and examined with a compound micro- 

 scope, it is found to be composed of countless numbers of bacteria and 

 broken-down plant tissue. 



Winter Habitat of Germ. — The germ of the organism, without 

 question, winters in the old lesions of the branches. Much work has 

 been done in making cultures at short intervals of time throughout the 

 year from the diiferent diseased tissues in order to see if the disease 

 organism was alive, and where it best could pass through the winter, or 

 dormant period. In every series of cultures the disease organism was 

 found, showing conclusively that the disease was still alive in the old 

 lesions of the wood and bark. The most prolific source of new infection 

 is the lesions on diseased twigs. Here the germs remain in almost a 

 dormant condition until the warm weather of spring, which arouses them 

 to a renewed activity, Avhen they exude on the surface, and are carried 

 to the new growth, leaves, branches, and nuts. From observation, the 

 young leaves seem to be infected very early, and probably are one of the 

 chief sources of the secondary infection. 



Secondary Infection. — The first, or initial infection, may occur on 

 only a few nuts and new growth, then quite suddenly the disease seems 

 to spread and infect many small nuts. This sudden increase of the 

 disease is due to an infection from the earlier diseased nuts and now 

 growth, and can thus be termed the secondary infection. 



Effect of Climate. — This disease is quite susceptible to variation in 

 climatic conditions. It is a matter of observation that the amount of 

 disease varies from year to year in a given locality, also that some 

 sections are freer from the disease than are others, even during the same 

 period of time. A grove may be very bad one year, and nearly free 

 from the disease the following year. The amount of moisture present 

 in the air has, without question, considerable influence on the quantity 



