386 BACTERIAL DISEASES OF PLANTS 



chlorid, otherwise known as corrosive sublimate or bichlorid 

 of mercury, is generally recommended for this purpose. It is 

 made up in the proportion of one ounce of the poison to one 

 thousand ounces of distilled water, clean rain water or boiled 

 well water. This may be applied as O'Gara recommends by 

 a sponge attached to the wrist or to the buttonhole by means of 

 a string about 2 feet long. The effectiveness of this germicide 

 is destroyed by contact with a metal container. It must be 

 kept, therefore, in glass bottles or wooden pails, never in tin 

 pails. Tools may also be dipped into 5 per cent carbolic acid 

 water or into 1 part of formalin diluted with 9 parts of water. 

 The hands must be kept out of both substances. For notes on 

 Reimer's newer germicides for fire-blight, consult Part I, page 71. 

 Eventually in this country the pear blight problem, which 

 is a very serious one, will be solved by discarding altogether the 

 susceptible French seedling stocks (Pyrus communis) on which 

 most of our valuable sorts are now worked, and substituting 

 resistant stocks. The most hopeful substitutes are certain East 

 Asian species, notably Pyrus ussuriensis, P. ovoidea, P. calleryana, 

 and P. variolosa. All of these species are very resistant to 

 Bacillus amylovorus, and the main question now appears to be 

 which are the most resistant, and which will prove most satis- 

 factory in other respects, i.e., grow equally with the graft, giv- 

 ing to it a firm union and a long life. For details the reader is 

 referred to F. C. Reimer's very interesting paper "Blight 

 Resistance in Pear Trees and Pear Stocks" (1916 Ann. Rept. 

 Pacific Coast Assoc. of Nurserymen. Also a separate pp. 1-8). 

 More recently (July 3, 1919) Mr. Reimer, who is superintendent 

 of the Southern Oregon Branch Station of the Oregon Agricul- 

 tural College Experiment Station (Post Office Talent, Oregon), 

 has written me as follows: 



"In my pamphlet I made the following statement regarding Pyrus ussuriensit;: 

 'This species appears to be immune to pear blight, at least under the conditions in 

 Southern Oregon.' 



"This statement was based on inoculation work performed with only a very 

 limited number of wild forms of this species. Since that statement was published 

 we have collected at this Station a very large number of types of this species and 

 have repeatedly inoculated them with the pear blight organism. The results based 

 on four seasons' work may be summed up as follows so far as Southern Oregon is 

 concerned: 



