30 



Karl Hermann Fernow 



Reliability of numerical results 



In interpreting the data, it is felt that too much reliance cannot be 

 placed on numerical results. Consideration must be given also to such 

 matters as the conditions under which the particular results were obtained, 

 and the clearness of the symptoms obtained. For example, the author 

 has no hesitation in stating that Nicotiana glutinosa is susceptible to 

 mosaic H, although only four positive cases were obtained out of seven- 

 teen plants inoculated. The symptoms were so different from those 

 obtained on this suscept when inoculated with mosaic B or mosaic D, 

 that the positive cases could not be regarded as contaminations. How- 

 ever, no such positive statement can be made concerning mosaic C on 

 this plant. It would appear that the three positive cases obtained with 

 this mosaic were contaminations, although this is by no means certain. 

 Taking all such factors into consideration, table 22 has been prepared to 

 show what interpretation is placed on the data by the author. Doubt- 

 less, further work will require changes in the conclusions, particularly 

 with reference to negative results. 



TABLE 22. Susceptibility op Species to Mosaics 



