202 Puget Sound Marine Sta. Pub. Vol. 1, No. 18 



kelp beds about Shaw Island are behind Canoe Island, near Broken Point, 

 and on several large submerged rocks some distance from the shore. The 

 largest of these rocks are: Reid Rock about midway between Shaw and 

 San Juan Island, another one about 200 meters off the southeast end of 

 Shaw Island and several others in a group southeast of Neck Point 

 (plate^ 34). 



Where the shore is muddy or sandy the algal vegetation becomes 

 very different from that of the rocky shores. Here the Laminariaceae 

 association disappears or is represented only by a few of its smaller mem- 

 bers. This is apparently due to the inability of the larger species to 

 find a place of permanent attachment on the sandy bottom. Eelgrass 

 (Zostera marina) is very common in shallow sandy bays, where it forms a 

 place of attachment for several smaller algae, especially Porphyra 

 naiadurn, which, together with the other algae which grow on shells and 

 small stones among the eelgrass, form the common algae of the Zostera 

 association. Rigg (loc. cit.) has already reported Agarum (fimbriatum) 

 and Laminarin {saccharina) as being common on shells and stones on the 

 sand and mud bottom of Blind Ba}^, Indian Cove and several smaller coves 

 along the shore. Agardhiella tenera, Costaria costata and several species 

 of Pterosiphonia and Polysiphonia are also found on shells and other ob- 

 jects where the bottom is sandy and clean. Ulva lactuca is the most 

 common alga in the more quiet muddy places, into which it often drifts 

 in large quantities, settling in beds sometimes even above the low tide line. 



Reefs that are exposed to the wind and waves are usually quite barren 

 when compared with the dense algal vegetation of the less exposed places. 

 This is very prominent along the reefs of the south and southwest shores, 

 on the rocks in Blind Bay and on Broken Point, all of which have a very 

 sparse littoral vegetation. Some of these places have practically no 

 Fucus, the few plants that are present are very small and appear as if 

 they had been ground off by the action of the waves. 



The north and west shores of the island are mostly very steep and 

 covered with timber close to the shore line so that the shore algae are 

 mostly in the shade at least in the afternoon. It is very striking to note 

 the density of the algal vegetation on these shaded rocks when compared 

 Avith similar places on the more barren sunny shores. In these shaded 

 places Fucus evanescent crowds up to the upper limit of the Endocladia 

 association, that is, clear up to the high tide line. Rhodomela larix grows 

 to be 30 to 50 cm. long in the shade in tiie upper littoral zone ; while or- 

 dinarily, in this region, it is a small scraggly plant 3 to 10 cm. long, grow- 

 ing in little tide pools. Leathesia dijformis, Soranthera ulvoidea, Micro- 

 cladia horealis, Ptilota pectinata, and several species of Odonthalia are 



