In many canes two such spores wouljl see- to show a rss-iltant effect 

 of the two stimuli so that both -YOU Id be half turned towards each other 

 with fe*VhlzOidal ceil showing a^tcTtake -a direction away from the - 



oK- iv*~-* 



light at resultant angle. 



T osenvinge ascribes this group orientation to a difference 



d>n the concentration of oxygen or of nutritive substances on the two 



forms on th > side 

 sides of the spore. He thinks the rhizoid^i'/ 4,/V/ 1 / toward 



of a group or towards another egg because the water on that side is 

 less rich" than on the outer side of the spores as a result o,' their 



/\ **u^A. 



metabolism, '"inkier (^ ) working with Cystoaeira barbata^that a dif- 

 ference in oxygen concentration ha? no such effect. Apparently the phe- 

 nomenon does not occur naturally in)thisjspecies since Wwr figure 

 given shows nothing but the effect of light. I have nevor seen a culture, 

 of Fucus evanescenjlth spOres germinating so near each other, which 

 s! owed only light orientation and ::ot the group orientation. aAl- 

 raost invariably when the spores- of this species germinate in such 

 close proximity, lipht appears to have no power to establish the po- 

 larity of the plant. 



The possibility that the group orientation is due to a pol- 

 arity established by the position of the egg in the oogoniura is 



tut*** 

 suggested by finding many groups of lying just as they escaped fror- 



the oogonial sac and conspicuously oriented with respe?t to each 

 other. The fact that groups of ten or of two are as regularly 

 oriented, would refute thT suggestion; but in order to prove that 

 the phenomenon is the resuljr of a stimulus acting after the eggs 

 leave the oogonium, a group of them were transferred to a watch crys- 

 tal and mixed with the point of a needle until their relative posi-fc- 



"/ions were entirely changed. But when they germinated the character- 

 istic orientation with respect to each other was found to be with- 

 out an exception. 



