1918 



Gail; on Fucus 



145 



2. Sporelings exposed to the air a part of each da}', growing under 

 different light intensities, 



3. Sporelings that had 3 weeks of good growing conditions, and 

 then were placed under different light conditions. 



The sporelings were grown in a south window on shells in a glass 

 dish. Oospores were obtained in the manner previously described. Por- 

 celain bowls 1 dm. in diameter were used as containers for seawater in 

 which the oospores were planted on shells and on microscopic slides. The 

 water on these sporelings was changed daily at 8 A. M. and at 2 P. M. 

 One series was placed in a south window and the other on an east shore 

 above a Fucus bed. In series number 1 of the above, in which the spore- 

 lings were submerged continually, the following conditions were tried : 



a. A bowl uncovered. 



b. A bowl admitting l/o light. 



c. A bowl admitting 1/4 light. 



d. A bowl admitting % light . 



e. A bowl covered so that no light entered. 



Table 3. Sporelings submerged in borcls all the time under 

 different light intensities 



The sporelings of series number 1 (table 3) were grown for about 

 4^ weeks. At the end of the first week of their growth, those receiving 

 no light were the largest; those receiving 1/^ light were next in size. 

 Little if any difference existed among those receiving all the light, 1/^ 

 light, and 1/4 light. The difference in size between those receiving less 

 light and those receiving more, consisted in greater length of the hold-fasts 

 of the former. At the end of the second week the sporelings receiving 

 only 1/8 light and those receiving no light were still longer, but the part 

 of the sporeling that develops into the plant body of those tliat received 



