1920] 



HURD—FUCUS SPORES 



37 



way was found of obtaining red light sufficiently intense which did 



by 



Wratten 



L 6 



green 



used before. The wave lengths to which each screen was permeable 

 were determined by means of a direct-vision spectroscope. The 

 experiment was then repeated, using the light from large north 

 windows facing an open field. Thus on the bright summer day 

 used for the experiments there was a maximum intensity of 

 indirect light available which had no disastrous heating effect. 



immediate 





The light orientation of 

 striking in the green and 



blue lights as in the control in white light (fig. 1), but entirely 

 lacking behind the red screen where the germination and develop- 



just 



Table II 



TABLE II 





Wave 



ESTABLISH THE 



POLARITY OF GERMINATING FllCHS SPORES 

 IN UNILATERAL ILLUMINATION 



Color of light 



Blue 



Green 



Red 



White (control) 



Wave lengths 

 transmitted 



\4000~SOOO 

 \6lOO-6300 



4800-6000 

 5800-7000 

 4000-7000 



Appearance of polarity 

 in sporelings 



+ 

 + 



+ 



indicates that from the limits of the visible blue to somewhere in 

 the green of the spectrum wave lengths of light can establish the 

 polarity of Fucus plants, while from this point in the green to the 

 boundary of the red they cannot (figs. 1, 2). Just where, in 



rm 



the green, light ceases to be effective could not be det 



with these screens. 



The intensities of these colored lights were not equal but the 

 red, as in any daylight source, was many times stronger than that 

 of the green or blue, and therefore it is all the more significant 





greater energy the long red 



the 



W can say definitely that 



