360 .LUMINOSITY IN PLANTS. 



spectrum than that of the higher fungi; and that in regard to the 

 light of fungi (and this is also true for insects) the green rays domi- 

 nate the weaker yellow and blue rays. I have actually succeeded in 

 distinguishing colors through the spectroscope in the intense light of 

 the previously mentioned Pseiidomonas lucifepa Molisch — green, blue, 

 and violet. This is the first established case where colors have been 

 seen through the spectrum in the light of a plant. 



It is possible to state, on account of the spectroscopic composition 

 of fungous light, that it may bo made to act on photographic plates. 

 In fact, the researches of various investigators — as Von Haren, Nor- 

 man, Forster, Barnard, and especially R. Dubois — have taught us 

 that photographs can be taken by bacterial light. If one uses in- 

 tensely luminous bacteria, such as are at my disposal, it is possible 

 to make photographs of bacteria colonies by their own light by an 

 exposure of five minutes, and if l)acteria lamps are employed, to make 

 good pictures of various objects, such as busts, thermometers, and 

 printed matter. In the last instance, however, to secure sharp pic- 

 tures, the time of exposure must be several hours. On the other 

 hand, if merely an impression upon the plate is desired, a single 

 second of time is sufficient to secure an image of a luminous-streak 

 culture. All pictures so far produced have been the resvdt of light 

 from colonies or mass cultures. But it appears to me not at all im- 

 ]3robable, in view of the practically unlimited sensitiveness of pho- 

 togra])hic plates, that hereafter it may be possible to photograph a 

 single bacterium cell by means of its own light, in the same way as 

 we have succeeded in rendering visible by means of the photographic 

 plate stars in the heavens which are invisible to the naked eye. 



The discovery of Rontgen-Becquerel rays and of the emanations 

 proceeding from radioactive elements make opportune the thought 

 that rays of particular quality uuiy also exist in bacterial light. Still 

 the assertion made by E. Dubois that bacterial light has the power 

 of penetrating opaque bodies, like wood and cardl)oard, is based 

 upon an illusion brought al)()ut through the direct action of the wood 

 or ])aper material on the salts of silver. On the same basis, I am 

 able to explain the remarkable, and from the standpoint of physics 

 utterly jiuzzling, statements of the Japanese investigator. Muraoka, 

 in regard to the light of the firefly. Fungous light — and the same 

 ii^ true of the light of the firefly — acts upon the salts of silver like 

 ordinary daylight, and is incapable of penetrating opaque objects. 



It seems to me to be not without interest that bacterial light also 

 brings about ]:)hysiological results in plants. Heliotropic sensitive- 

 ness is, according to Wiesner, of remarkable intensity, especially in 

 the case of the etiolated seedlings of certain plants. Such plants can 

 discriminate better than th(> human eye betw(HMi the most minute dif- 

 ferences in light intensity and may therefore with justice be con- 



