142 Pub. Puget Sound Biol. Sta. Vol. 2, No. 43 



Even a very casual observation shows that Fucus is not abundant on 

 a gravelly beach. When it does occur in such a habitat it is nearly always 

 found on boulders or firmly j^lantcd rocks which project above the surface. 

 There are probably two factors which make the growth of much Fucus 

 on gravel impossible: 



1. The movement of stones by the action of the tides, thus causing 

 the oospores to be rubbed off. 



2. The smoothness of the stones, thus causing them to become thor- 

 oughly dry during low tide and interfering with germination. 



It is possible that decomposing plant and animal deposits on flat 

 beaches with little movement of gravel affect Fucus unfavorably. Three 

 attempts were made to grow the oospores of Fucus on smooth beach stones 

 and shells between the low- and high-tide lines. Fucus plants containing 

 large, slimy fertile tips were secured in the evening from Fucus beds. 

 These were wrapped rather tightly in a towel and left there over night. 

 In the morning they were unwrapped and dried in a room for 30 minutes. 

 The tips containing the conceptables were broken from the plant body 

 and placed in a battery jar containing seawater. In about 10 minutes 

 Ihe oospores were discharged. In 30 minutes the oospores had settled to 

 the bottom of the jar, and the plant-tips, together with all but a very 

 small amount of the water at the bottom of the jar, were poured off. 



Shells of average size, and white, smooth stones, were placed in a flat 

 porcelain pan and covered with seawater. A pipette was used in planting 

 the oospores on the shells and stones. They were then left quietly in the 

 pan for 48 hours. The water was changed on the second day by means 

 of a rubber siphon. After 18 hours the sporelings usually were 10-celled, 

 and were securely fastened to the stones or shells by a layer of muci- 

 laginous substance. Stones and shells were planted under various condi- 

 tions. All were fastened to the substrata to prevent the sporelings from 

 being rubbed off. A series of experiments was begun as follows: 



1. A shell and a stone were placed on the beach. 



2. A set of each was placed in a Fucus bed. 



3. A set was placed under the crate that received 1/^ light. 



4. A set was placed under the crate that received 1/4 light. 



5. A set was placed under a crate that received % light. 



6. A set was placed under an inverted tub, under which was total 

 darkness. 



The first set of sporelings on the beach disappeared, rocks and all, 

 one week after they were started. However, they were not growing. 

 Two other sets were started at once. These did not grow and had dis- 

 appeared from both stones and shells by the eighth day. Observation 

 showed that the smooth stones and shells were dry for two or three hours 



