1915 Sheldon; on Nereocystis 17 



The stipe of Nereocystis often floats out for many feet on the 

 surface of the water and sunburn follows. One side of the large, over- 

 wintered plant mentioned below showed this very clearly. Many other 

 examples were found, especially after an extremely low tide. During 

 the weeks of work in the kelp bed the writer noticed that shortly after 

 "sunburn" took place decomposition followed. The over-wintered plants 

 showed decomposition in practically all of the "sunburned" spots. In 

 measuring kelps that were badly "sunburned,' in the three cases observed, 

 no growth of the stipe was found. Just why certain kelps "sunburn" and 

 others do not was not determined. It will thus be seen that many spec- 

 imens measured for experiment were of no use. Decomposition often 

 set in as a result of bruises caused by the plants being jammed between 

 logs, boats, etc. 



In addition to those measured in above table, one whose stipe was 47 

 feet 3 1/2 inches in length was also measured. This individual plant 

 was one which had matured the year before, but survived the winter. No 

 growth at all was found. Its holdfast had been loosened from the bottom 

 of the sea and the plant was found floating along the edge of the kelp 

 bed. It was covered with diatoms, Antithamnion floccosum, Porphyra 

 nereocystis and other algae. 



In the latter part of August a set of experiments was arranged to 

 show the effects of mutilation, and to show the region of greatest growth. 

 The observations on these were made by Mr. Donald Clark, a junior 

 student in the University of Washington. These last experiments were as 

 follows : 



On August 23, two healthy kelps, the first measuring 26 ft. 5 in., and 

 the second 28 ft. 3 in., were cut in two parts exactly 3 ft. below the base 

 of their laminae. The openings of the hollow stipe were then corked se- 

 curely. Three weeks later measurements showed a 3 in. growth from the 

 base of the laminae to the 3 ft. cut in the shorter specimen. Decomposi- 

 tion had partially destroyed the remaining portion of the stipe. In the 

 case of the longer kelp, the amount of growth in the 3 ft. piece was not 

 enough to measure. There was also no growth in the remaining part of 

 the stipe. Decomposition was very evident here also, but organism 

 may not be the sole cause of death. Rigg (U. S. Senate Document No. 

 190; Fertilizer Resources of the U. S,, pp. 185-186, 1912.) reports that 

 experiments by Zeller show that the stipe dies when the laminae are 

 removed. The small cut surface in that case makes death from decompo- 

 sition unlikely. 



A second pair were cut in the same way as the above two, but the 

 corking of the cut region of the stipes was omitted. One of these kelp 



