BULLETIN 231] WALNUT CULTURE IN CALIFORNIA. 355 



Puncture Inoculation. The puncture experiments shown in the pre- 

 ceding table were on young growing shoots with culture from potato 

 cylinders after three ,to five days' growth. These experiments give 

 almost uniformly positive results. During the past two seasons many 

 such inoculations were made and a few of these are summarized in the 

 preceding table. Many other cultures of yellow organisms that some- 

 what resemble the walnut blight growth were also tested, but with nega- 

 tive results. The table shows, furthermore, that cultures isolated from 

 pith, wood, bark, nuts and leaves all produced the typical blight lesions. 

 In several instances cultures that had been grown on artificial media one 

 and two years gave positive results from puncture inoculations. 



MORE DETAILED ACCOUNT OF INOCULATION EXPERIMENTS. 



The following description gives more detail regarding certain of the 

 more suggestive experiments : 



1. Puncturing of Nuts. April 2, 1907, seven young nuts were inocu- 

 lated by puncture with a sterilized needle carrying germs from a pure 

 culture of walnut blight. April 12th five of the nuts were still attached, 

 and all showed infection at every place where punctured. 



2. Contact Inoculation. April 2, 1907, six small nuts were inculated 

 by simply placing the sticky bacterial growth from a pure potato culture 

 in contact with the nuts without making a puncture of any kind. April 

 12th four of the nuts were still attached and showed positive infection 

 at points of inoculation. 



3. Atomizing Nuts. From culture isolated about six months previ- 

 ously and cultivated .during the meantime in artificial media. April 12, 

 1907, 5 p. m., eight small nuts were atomized with culture from potato, 

 eight days' growth. The day had been cloudy most of the time and 

 was still cloudy when the experiment was made. April 30th six nuts 

 were attached, three of them healthy and three diseased at one or two 

 points. May 9th six nuts were attached and four of them had one or 

 two points of infection. A shoot inoculated at the same time by punc- 

 ture showed positive infection. 



4. Atomizing nuts from culture of 'blight isolated from diseased new 

 growth. April 16, 1907, six small nuts were atomized with six days' 

 growth of organism on potato cylinders. This culture was originally 

 isolated from blight on new growth. May 9, 1907, the six nuts were 

 still attached and showed fine positive results with many points of 

 infection. Is the use of a culture recently made from blight on new 

 growth the cause of so fine positive results ? 



5. Atomizing nut by using solution of water and diseased tissue. 

 April 27, 1907, six small nuts on a late blossoming tree were atomized 



