1918 



Gail; on Fuciis 



147 



were at first larger than those receiving all the light or 1/4 light. How- 

 ever they soon lost their dark brown color and ceased to grow, while the 

 sporelings receiving light had a dark brown color and grew. This again 

 points toward the necessity of light. It does not show that aeration is 

 helpful or detrimental. The desiccation of the sporelings on the smooth 

 slide was probably more severe than they would have received on the 

 rocky shore. 



Table 5. Sporelings three weeks old grown on shells in normal 

 light, then continued under different light conditions 



In series number 3 of the above in which the shells bore healthy 

 sporelings three weeks old, 3 conditions were tried (table 5). The oospores 

 were germinated in a south window in an uncovered glass jar. These 

 sporelings were then subjected to different light intensities as follows: 



a. A glass jar uncovered. 



b. A porcelain bowl admitting I/2 light from above. 



c. A porcelain bowl admitting no light. 



At the end of 2I/2 weeks the sporelings in the open glass jar were 

 twice the size and much healthier in color than the sporelings receiving 

 1/2 light. The sporelings which received no light had died. This shows 

 that light is necessary even after the sporelings have attained a consid- 

 erable size. The sporelings in the open glass jar had a protuberance on 

 one side which may have been the beginning of the dichotomous branch- 

 ing characteristic of Fucus. 



Sporelings 48 hours old were attached to shells that were fastened 

 to cords each 7 meters long. The shells were fastened like those with 

 young and mature plants and were suspended in the sea. There were 4 

 cords suspended. The shells were examined under the microscope once 

 each week. At the end of the fourth week a difference was noted in the 

 color of the sporelings; the deeper the submergence the lighter the color. 

 Some had disappeared from tlie shells, probably having died. At the end 

 of the fifth week (table 6), all of the sporelings had disappeared from one 

 cord except four on the shell 3 dm. from the surface. One of these 



