1920] HURD—FUCUS SPORES 35 



the first four hours of illumination and cannot be changed afterward 

 by any change in the direction of the incident light. He concludes, 

 therefore, that light can orient the spore only during fertilization. 



Peirce and Randolph (18) performed one-sided illumination 

 experiments with Dictyota, Dictyoptcris, Laurencia, and Cystoseira, 

 and pointed out the certainty of the action of other factors besides 

 light, because rhizoids are formed in the dark and in all-sided 

 illumination. They said that although Winkler (21) suggested 

 the possibility of stopping germination by changing the direction of 

 light every three hours, it could not be done with Dictyoptcris . 

 They emphasized the possibility of influences preceding the 

 illumination affecting the polarity. Later, Peirce (17) demon- 

 strated this same phenomenon, that is, the orientation of the first 

 cleavage plane and the establishment of the apical and basal cells 

 by light, with spores of Anthoceros, Fimbriaria, and Gymnogramme. 



The work of Fromme (8) on the urediniospores of Puccinia 

 rhamni is interesting because it refutes the idea that the orientation 

 of the sporelings by light is due to the power of one-sided illumi- 

 nation to cause an aggregation of chloroplasts. He said that 

 in darkness the germ tube grew from any side of the spore, but 

 that in unilateral light the tubes almost always issued from the 

 darker side of the spore. 



In order to obtain an abundance of spores for experimental 

 work, the following procedure suggested by Dr. N". L. (iArdner 

 was followed. The fruiting plants of Fucits injlatus 2 were collected 

 at Sausilito at low tide one day and kept overnight in damp news- 

 papers. The next morning they were dried slightly by exposing 

 them to the air for from 15 to 30 minutes. The bruiting tips were 

 then cut off and submerged in sea water in the culture dishes. 

 After about 15 minutes many eggs and sperms settled to the 

 bottom of the dish, or could be scraped off into the water, and the 

 piece of plant was then removed. The fact that Finns injlatus is a 

 monoecious species makes it impossible to tell the exact time of 

 fertilization, but it occurs soon after the eggs escape from the 

 oogonial sac into the water. The sperms at this time can be seen 



2 Although the identification of this species is nut certain, it is thought by Dr. 

 X. L. Gardner to be most probably Fucus injlatus. 





