540 



SCIENCE 



[N. S. Vol. LII. No. 1353 



as if to alight again. When it seems that they 

 must inevitably terminate their flight and 

 settle down upon the herbage, another flash 

 renews and quickens the flight impulse and 

 they arise precipitately, as if suddenly pro- 

 pelled upward by some energizing stimulus at- 

 tending the flash. 



, This striking behavior may be observed al- 

 piost any calm evening throughout the sum- 

 mer. It is particularly noticeable when the 

 insects are arising from the herbage, and are 

 just preparing to get fairly on the wing. What 

 is the actual significance of this luminosity to 

 .the insects? In what manner does the flash 

 ■stimulate momentarily the powers of upward 

 flight? It would sometimes seem as if the 

 energy-transformation attending the flash, 

 actually aided them to get fairly on the wing, 

 .possibly also sustaining their flight in some 

 manner. 



H. A. Allard 

 Washington, D. C. 



SPECIAL ARTICLES 



FUNGICIDAL DUSTS FOR CONTROL OF SMUT 



Fob more than a century eflforts have been 

 made to secure a perfect method of treating 

 cereal seeds to destroy smut spores carried on 

 their surfaces. Many fungicides have been 

 tested and a number of standard formulas 

 have been put forth as efiicient. More recent 

 investigations have demonstrated that none 

 of the formulas involving dipping seed in 

 solutions, fumigating with powerful gases or 

 dissolving spores by various solvents, has 

 proven completely successful. Reagents of 

 sufficient strength to destroy the smut spores 

 have proven to be injurious to the germina- 

 tion of the seed. 



It 'has been demonstrated recently by the 

 writers and by many other investigators, that 

 the commonly accepted standard smut fimgi- 

 cal formulas involving the use of bluestone 

 and of formaldehyde, are frequently extremely 

 injurious to the germination of the seed and 

 the development of the seedlings. In arid 

 and semi-arid wheat areas, formaldehyde 

 frequently causes serious losses in seed 



planted in dry soil. Bluestone, the preferred 

 fungicide in such regions, causes serious losses 

 in germination and delayed growth of seed- 

 lings. Threshing operations in semi-arid 

 regions cause greater rupture to seed coats 

 than occur in more humid regions, further 

 increasing seed injury. To avoid these losses, 

 it has been recommended that the bluestoned 

 seed be dipped, after a short drain, in a lime 

 solution to react with the copper and thus 

 check the penetration of the copper sulphate 

 in the seed germ as soon as it has destroyed 

 the bunt spores adhering to the surface of 

 seed. Unless the seed coats have been badly 

 ruptured this formula is very effective but it 

 has been found that the seed does not pass so 

 freely through the drill and, in cold damp 

 weather, the seed dries slowly due to the coat- 

 ing of lime and hence may cause fermenta- 

 tion or heating. To avoid these troubles ex- 

 periments with bluestone used as a dust were 

 undertaken. The partial success of flowers 

 of sulphur in preventing bunt in California 

 and the reported success with copper carbonate 

 by the Department of Agriculture of New 

 South Wales, gave encouragement for at- 

 tempting dust treatments. 



Little Club wheat dusted with spores of 

 bunt (Tilletia tritici) at the rate of 1 part of 

 spores to 750 parts of seed by weight and 

 treated according to standard formulas, gave 

 the following results: 



Check 



Formaldehyde 



Copper sulphate . . . 



Copper sulphate t 1-4 



"1- lime solution 



Copper carbonate 



Copper sulphate 



Copper sulphate dust mixed 

 with calcium carbonate 

 dust (1-1) 



Copper sulphate and lime 

 dusted separately 



6.2 



0. 



0. 



Rod row plantings were made March 8, 

 1920, and later, which accounts for the rather 



