in. TROPIRTIC REACTIONS TO MONOCHROMATIC LIGHT IN FUCUS 



SPORELINGS. 



The power of external factors to determine the polarity of 

 a germinating spore is, without doubt, the power to orient the spin- 

 dle of the first dividing nucleus, if that polarity is established 

 by the direction of tne first cleavage plane. The work on such 



orientations is very, limitedjaml has often resulted in negative resuWs 



/ &fy<~MtcJL/$j. ^/S^-iL^f/^^. 



^kjjito<-JT~-\ ^2-c*u) woril^U**^ o fr gfl S' 9 ' eggs 



,'/\ -j^r |r - - f* 



-omoryo QJ subjecting *aasQ.o pressure. The spindle parallel to the 

 flattened sides of the egg. This is consistent with Hertwig's theory 

 that the spindle. should form pareifcel to the longer aocis ofl a 

 iding cell. It is conceivable that the power of light to orient <*- 

 tfe* spindle might result from its power to cause more rapid growth 



<-O-^L*^O-v. -v--v^^-^--T -*1*u^-l<"Vl,^ V 



along one axis, with tho rtfeult thayche elongated celljin turn * 

 orients the spindle No such effect of light has been demonstrated 



with animal eg,^s? but in certain pi an ts . vi z . , Equi se turn , Fucus .Pi c- 



o^v^f( C/i<-ocxxw<xOc * 



fystoseira,, it has been found that one-sided 

 'A 



illumination with daylight causes the first cleavage plane to be 

 formed perpendicular to the direction of the incident light and the 

 cell on the darker side of tne spore to become the rhizoidal cell. 

 Equal illumination on all sides retards or prevents germination. 

 Gravity add contact cannot establish the polarity of these spores. 



All these experiments were conducted witr natural light as the 

 source of illumination. The first purpose of the present investi- 

 gation ?/as to determine tne ower of monochromatic light to es- 

 tablish the the polarity of germinating spores of Fucus evanescens. 



It was hoped that the results o4 such experiments might give a clue 



Y> W 



to the mechanics of aZuA orientations. If all wave lengths should pre- 



s\ 



duce the same effect it might be the result of a general inten- 

 sity gradient; if only the blue ligho is effective, the problem 

 is one of a chemical effect; if only the red it might DC assumed th*"t~ 



