606 



SCIENCE. 



[N. S. Vol. XVlll. No. 4G2. 



frangibility produce greater decoloring effect 

 than those of high refrangibility, but from 

 the results obtained here it would seem that 

 decoloration is in no way directly or inversely 

 proportioned to refrangibility. It will be 

 seen that the blue and the red are close to- 

 gether here, while in the solar spectrum they 

 are far apart. 



In the accompanying Fig. 2, I is given the 

 curve of decoloration of an alcoholic solution 

 of chlorophyll with the screens already de- 

 scribed. The vertical lines represent relative 

 quantity of effect— d^ darkness; r, red; y, 

 yellow; g, green; v, violet; w, weak diffused 

 light. In Fig. 2, II is given the curve for rela- 

 tive phototropism. In both cases no attempt 

 is made to represent the actual difference be- 

 tween any two as compared with any other 

 two, e. g., in Fig. 2, II, blue is three units 

 above green simply because it happens to be 

 stronger (in effect) than diffused light, which 

 is stronger than violet, which is stronger than 

 green; nor is it intended that the ' colors ' in- 

 dicated shall be in the exact position of the 

 spectrum, though so far as the ' colors ' are 

 concerned they are in that order. 



In nearly all the experiments the apparatus 

 was indoors, and the light exposure chiefly 

 north. Some light came from the east and 

 about an equal amount of exposure toward the 

 west. The first experiments were made in the 

 greenhouse, but it was found that too much 

 heat was produced, resulting in the wilting 

 and even in the death of the plants. How- 

 ever, so far as carried on, the results were 

 identical with those under diffused light. 



The plants which proved most susceptible 

 to phototropic influences were barley, wheat 

 and tobacco seedlings. The best, most posi- 

 tive and the quickest results were obtained with 

 wheat and with barley seedlings from five to 

 forty mm. high. Other seedlings used were 

 Catalpa, Datura, bean, pea, corn, sunflower 

 and pumpkin. 



No attempt is here made to deduce a phys- 

 iological or a physical law from these phe- 

 nomena because it is thought that sulSciefit 

 data are not yet at hand; nor is therp-'^^.iy 

 quantitative effect estimated as exist' ^1?^ be- 

 tween any two of the screens used, fr is quite 



clear, however, that the statements of Sachs 

 and others, namely, that the effect, whether 

 phototropic or bleaching of chlorophyll 

 solution, varies as the refrangibility, is not 

 correct. It may be, however, that had the 

 formulae of their screens been given, it might 

 be possible to see how they arrived at their 

 results. 



On looking at the spectra of the screens here 

 given it may be seen that the blue permitp 

 considerable of other ' colors ' to pass through, 

 especially red. Now, since the phototropic 

 effect of blue is greater than that of diffused 

 daylight, the conclusion naturally follows that 

 some portion of the solar spectrum is nega- 

 tively phototropic because the blue as well 

 as the other ' colors ' passes through window 

 glass. The question at once is suggested then 

 as to where in the spectrum this negative 

 portion is ; but seeing that all the ' colors ' here 

 given are positively phototropic, the one con- 

 clusion is left, and that is but a mere sugges- 

 tion, namely, that it may occur in those 

 darker bands in the blue represented by the 

 sharp down curve in its spectrum. 



It is the intention of the writer to investi- 

 gate this point by securing screens as nearly 

 as possible corresponding to those portions of 

 the spectrum; and at the same time to ex- 

 amine other intervening ' colors.' 



J. B. Dandeno. 



AGBICtlLTURAL COLLEGE, MiCH. 



SCIENTIFIC NOTES AND NEWS. 



At the last meeting of the Rumford Com- 

 mittee of the American Academy of Arts and 

 Sciences, the sum of three hundred dollars 

 was granted to Professor W. J. Humphreys, 

 of the University of Virginia, in aid of his 

 research on the shift of spectrum lines due 

 to pressure; and the sum of two hundred and 

 fifty dollars to Professor N. A. Kent, of 

 Wabash College, in aid of his research on the 

 circuit conditions influencing electric spark 

 lines. 



Dr. Carlos J. Findlay, of Havana, well 

 known for his work on yellow fever, has been 

 elected president of the American Public 

 Health Association. The next meeting of the 

 association will be held in Havana in April. 



