NOTES ON NEREOCYST1S 89 



Since the bulb of mature specimens of this plant is always at 

 the surface of the water, the fronds in which the photosynthetic 

 tissue is evidently located are kept just beneath' the surface in a 

 situation favorable for the maximum amount of light that could 

 be obtained without exposing the fronds to the drying influence of 

 the air. The penetration of light far into the water is a factor in 

 the distribution of this species only during its very young stages. 



The combination then of a rocky bottom, a strong tideway and 

 suitable depth of water is necessary for the production of a large 

 Nereocystis bed. The combination of these conditions is most 

 frequently found on ledges of rock along the shore. There is a 

 narrow fringe of kelp along a large part of the shore line of the 

 San Juan Islands. Much of this fringe does not exceed 8 m. in 

 width, but at Kanaka Bay on the west side of San Juan Island and 

 at Iceberg Point at the southern end of Lopez Island the beds 

 broaden to 100 m. or more. Navigators in this region feel safe in 

 running their boats close to the outer edge of the kelp beds, know- 

 ing that where the kelp ceases to be seen it means a sudden in- 

 crease in the depth of the water. In the case of the Smith Island 

 bed the ledge is so extensive that the bed is about 1800 m. square. 

 The beds are extensive also along the American shore of the strait 

 of Juan de Fuca, especially in the vicinity of Cape Flattery and 

 Neah Bay where they attain a width of 200 m. in some places. 



Not all the kelp beds, however, are found along the shore. A 

 shoal with a rocky surface frequently furnishes the conditions for 

 the production of a large bed. Examples of this are found on 

 Dennis shoal west of Allan Island, on West bank north of Orcas 

 Island, and on the shoals north of Patos Island and on those north 

 of Sucia Island. Dall 6 reported in 1875 that there was a bed 

 of "bull-head kelp" (Nereocystis?) 25 square miles in extent on 

 a shoal in the open sea north east of St. George Island in the Bering 

 sea. Nearly all of the Nereocystis beds of the Puget Sound region 

 are what the foresters would call a "pure stand," but in the vicin- 

 ity of Neah Bay some of the beds are mixed with Egregia menziesii 

 and Macrocysiis pyrifera on the side toward the shores. 



6 Dall, W. H. Arctic marine vegetation. Nature, 12: 166. 1875. 



THE PLANT WORLD, VOL, 15, NO. 4, APRIL, 1912. 



