10 March, 1916.] The Walnut. 161 



of Californian walnut groves would be extremely difficult, if not abso- 

 lutely impossible, for the average grower to get the work done thoroughly 

 enough, even though the spraying done by ourselves should prove ex- 

 tremely effective in controlling the disease. During the summer follow- 

 ing our sprayings careful observations were made from time to time of 

 the conditions as to blight of the sprayed and unsprayed trees in the 

 experimental orchards. From such observations no difference whatever 

 in the prevalence of the disease on the nuts could be detected. Many of 

 the sprayed trees lost a large portion of their crop from bacteriosis, and 

 even on individual, rather small trees, or individual branches which had 

 been especially well sprayed, and absolutely covered with the mixture, 

 much blight developed on the nuts, and it soon became apparent that no 

 satisfactory degree of control, if any, had been secured by our work. 

 During the following year, 1907, the appearance of the trees sprayed in 

 1906 gave some reason to believe that the disease was less prevalent on 

 the sprayed than on the unsprayed trees. This was particularly true 

 in the case of trees sprayed with lime-sulphur. It is, therefore, not 

 improbable that while infection of the nuts during the year when the 

 spraying was done was not prevented, that the shoot and twig infection 

 was somewhat controlled, and that on this account less blight was 

 carried over winter, and less nut infection took place the following 

 year. From the experiments, we became thoroughly convinced that 

 the possibilities of walnut bacteriosis control did not lie in the direction 

 of spraying.* 



* 'The re-iult-s of sprayin? in Victoria gave no satisfaction as regards controlling this disease. 

 Furthermore, It Is not a practicable proposition owing to the size the trees attain under favorable con- 

 ditions. — Author. 



NITROGENOUS NODULES. 



The majority of plants do not have root nodules, as, for example, 

 the cereals, potatoes, and the like. The nitrogenic nodules are pro- 

 duced by micro-organisms closely related to the bacteria, which make 

 their entrance from the soil through the tender walls of the younger por- 

 tions of the roots, and induce a cell growth in the region of the invasion 

 that results in a nodule, which is able to lay hold and adapt the free 

 nitrogen of the atmosphere for the use of the plant. To a certain ex- 

 tent the number and size of the nodules may be taken as an index of 

 the success of the plant. Soil from an old pea field will produce nodules 

 upon pea roots in new land better than upon clover or any other crop. 

 This leads to the subject of soil inoculation. Successful experimenU 

 have been made in soil inoculation with crimson clover and hairy vetcli. 

 Soil from old pea land has made a striking difference when spread upon 

 other soil, and the larger growth and deeper green colour of the }>oa 

 plants. Soil in which peas were grown in one district lias been brouglit 

 to another for inoculation, and the nodules formed in tliis mixture were 

 afterwards used to inoculate other soils. Besides this also the growtli of 

 leguminous plants in rotation with cereal crops fulfils another important 

 function in the promotion of humus on the surface soils. 

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