October 12, 1917] 



SCIENCE 



361 



has not wished for a standard series of sym- 

 bols. The question is not a new one; it was 

 considered by a committee of the American 

 Association for the Advancement of Science 

 many years ago, but its efforts were shattered 

 in the attempt at international cooperation. 

 Such cooperation is very desirable, but if it 

 is not available that is no reason why America 

 should deny herself the benefits of ceordina- 

 tion which she, with her scientific resources, 

 may devise. Every monograph, evei-y text- 

 book that is written adds to the confusion of 

 symbols, for there are no standard tables to 

 guide one. It seems to me not only possible, 

 but practicable that a list of symbols could 

 be compiled under various headings — mathe- 

 matical, astronomical (with subdivisions), 

 physical (with subdivisions), geophysical, 

 electrical, etc. The various headings would 

 be necessary because the same symbol is fre- 

 quently used under different headings, and, 

 of course, with different meaning. Whether 

 we write g for terrestrial acceleration or a is 

 fundamentally quite immaterial, so it is 

 whether we write L, or 0, or >^ for latitude, 

 but it is not immaterial for the person who 

 reads it. He will probably wonder why the 

 writer doesn't use such and such sjrmbol. We 

 want uniformity, uniformity to as great an 

 extent as possible. Personal preferences 

 should be waived and sunk in the greater 

 scheme of uniformity. There are already 

 many constants, many expressions, many con- 

 cepts that await being labeled for common rec- 

 ognition. Who is to undertake this work, who 

 is to do the labeling? I can see, or rather I 

 can hear rumbling — " I'm not going to be 

 bound by any such tables." Quite so, they 

 would have no authority whatever. How- 

 ever the dictates of common sense would be 

 their propelling force and I think the vast 

 majority of American scientific writers would 

 avail themselves of their usefulness. Any- 

 thing that promotes readiness of understand- 

 ing and ease of reading mathematical expres- 

 sions and equations should be encouraged. 



In order to give definiteness to my ideas, 

 which I hope will arouse discussion, I would 

 suggest that the tables of symbols spoken of 



be prepared by the Carnegie Institution of 

 Washington. It is work that so eminently 

 falls within its scope, and it is so well equipped 

 with material and other resources, that one 

 can look forward with confidence to a well- 

 matured publication. Should the work be 

 imdertaken by the Carnegie Institution 

 nothing would further the general adoption of 

 the symbols promulgated more than the wide 

 distribution of the publication and that could 

 be profitably effected by sending to every sci- 

 entist — to every man in "American Men of 

 Science " — gratis a copy of the Carnegie pub- 

 lication. 



My closing word: Don't let details smother 

 uniformity. Make a start. Otto Klotz 



Dominion Obsbrvatost, 

 Ottawa, 



August 4, 1917 



BACTERIAL LEAF SPOT OF TOBACCO 



A bacterial leaf spot of tobacco has been 

 found to occur within certain sections of 

 North Carolina. This disease, because of the 

 rapidity with which it spreads, has appropri- 

 ately been given the name " wild fire." It 

 first manifests itself in seriously destructive 

 form at the time of transplanting, so that in 

 some fields it has been necessary to replace 

 the seedlings by a second and a third trans- 

 planting. Plants in the seed beds from which 

 these seedlings were taken have been found to 

 be diseased, indicating that the malady was 

 introduced from the seed beds. 



The disease first appears as circular yellow 

 spots about 1 cm. in diameter. A minute 

 brown area indicates the center of the spot. 

 Within a few days the brown area will have 

 enlarged to 2 or 3 cm. in diameter with a 

 translucent border and surrounded by a wide 

 chlorotic halo. When the spots are numerous 

 they fuse, forming large brown irregular areas 

 which in severe cases involve most of the leaf 

 tissues. 



Isolation and inoculation work has shown 

 that the disease is due to a grayish white bac- 

 terial organism which is heretofore unde- 

 seribed. This organism is rod shaped, about 

 three times as long as wide, and actively motile 



