1918 Gail J on Fucus 143 



during low tide each day, while the rock upon which Fucus grew was 

 moist in the angles and cracks. The sporelings were not able to withstand 

 these severe periods of desiccation. This seems to be a strong factor in 

 almost excluding P'ucus from the beaches. 



The stones and shells serving as substrata for the sporelings in the 

 Fucus beds, as well as those underneath the crates which received % and ^ 

 light, were moist for longer periods than on the beaches. However suffi- 

 cient moisture was not retained on their smooth surfaces to produce growth 

 in the sporelings and they were lost from the shells on the 15th day. 

 Since the sporelings died among the Fucus beds at about the same time as 

 under the crates, light cannot be considered a very important factor here. 

 The sporelings attached to shells and stones under the crate receiving l/g 

 light grew for about three weeks. They gradually lost much of their 

 color and lost all symptoms of growth ; but they w'ere still attached to 

 both the stones and the shells at the end of five weeks. They probably 

 grew until the reserve food of the oospore had been exhausted, together 

 with whatever food the plant was able to manufacture under the reduced 

 amount of light. The food requirements of the young plants were proba- 

 bly too great for the conditions ; thus growth ceased and death would un- 

 doubtedly have followed. 



The sporelings attached to the shells and stones under the inverted 

 tubs grew for about a week only. Apparently when the food stored in 

 the oospore was used up, growth ceased, since photosynthesis could not go 

 on in total darkness. At the end of the 8th day they had become much 

 lighter in color, and no more growth could be detected. By the end of the 

 third week some had been lost from their substrata ; and by the end of the 

 fourth week none could be found. Under the crate receiving 1/g light, 

 and under the inverted tub, evaporation was reduced to such an extent 

 that they had sufficient moisture for growth; but the light was so reduced 

 that probably the necessary food could not be manufactured since death 

 resulted. 



To study the effects of submergence, young plants that had about 

 two lobes, and also mature plants, were suspended in the sea at diifcrent 

 depths. Chips of rock to which the Fucus plants were growing naturally 

 were secured. The locality was just off shore from a Fucus bed. The 

 depth of the water at the spot was about 9 meters. Heavy cords each 7 

 meters long were used. Rocks containing the Fucus plants were fastened 

 to the cords at intervals of 3 dm. for the first 3 m. from the surface. 

 Below 3 m. the rocks containing the Fucus plants were fastened at in- 

 tervals of 6 dm. Two cords containing young plants and two containing 

 mature plants were suspended. These were examined once each week. 



