316 Pub. Puget Sound Biol. Sta. Vol. 2, No. 53 



plants which they have examined correspond to the slender form from 

 European waters. 



This narrow form^ corresponding to the descriptions of the European 

 type, has been collected for years by members of the Puget Sound Biolog- 

 ical Station;, on the rocky shores off Kanaka, Bay, on the seaward side of 

 San Juan Island. The writer has examined specimens in the Station 

 herbarium and in private collections, and in the summer of 1918 was 

 fortunate enough to secure an abundance of excellent material. The plants 

 were growing on the most exposed point of a steep rocky headland, 

 where strong tidal currents continually sweep along shore, and the heavy 

 surf or ground swell from the open Strait of Juan de Fuca continually 

 breaks on the rocks. Collections were made by hand, with the greatest 

 difficulty, at extreme low tide, as the plants were anchored to the per- 

 j^endicular faces of great rocky ledges where they were continually sub- 

 merged, even during the lowest tides. 



Early English writers describe the species as varying from two to six 

 feet in length, about 60 cm. to 2 m., but the writer found no specimens 

 exceeding 60 cm. However, the main axis and all the longer branches were, 

 without exception, frayed at the ends, due no doubt to the beating of the 

 plants against the rocks by waves and currents. 



The holdfast is not smoothly conical, as in other species examined, 

 but roughly lobed, not only around the circumference, but also over the 

 upper surface, and is much larger than in other species. From about the 

 center of this rough, irregular holdfast arises a single frond with stipe 

 almost cylindrical at the base, but widening immediately, or within 2 or 

 3 cm. at the most, into a flattened thallus. The main axis reaches an 

 extreme width, in the fresh plant, of 6-8 mm., and is closely and regularly 

 pinnated, at distances varying from 2-8 mm., with opposite distichous 

 branches, which vary extremely in length. Short branches alternate with 

 long without definite sequence, although in general the larger branches 

 are toward the base. Usually both branches of a pair reach about 

 the same stage of development, barring accident, indicating some corre- 

 lation in growth. The shortest branches are simple, from a few millimeters 

 to one or two centimeters in length, dentate along their margins and com- 

 paratively few. From< these simple structures up to the longest branches, 

 which may be 30 to oO centimeters long, and several times pinnate, all 

 degrees of development are found. Branches of all orders narrow down 

 to a slender cylindrical base, and taper to a long point at the extremity. 

 The margins of all the pinnules are sharply and finely dentate, the teeth 

 bearing, early in the spring, tufts of slender branching filaments which 

 are shed later in the season. Toward the base of the frond the midrib is 

 very prominent. In fresh or formalin material it stands out as a distinct 



