peters: causes that produce "bald-headed" kelp. 7 



pending loss and to continue eating toward the base until the 

 whole frond was gone. The appended table of some observa- 

 tions gives color to this conclusion. 



From the table it is seen that the snails are found on the 

 kelp where the current is weak, that in these places many 

 plants are without fronds, that the kelp in the strong currents 

 have relatively few without fronds and that where they do 

 occur they are in clustered groups, and that where the plants 

 are scattered and in strong currents they are uniformly 

 healthy. 



In observation No. 23 the plants were against the shore, 

 so that as the tide ebbed and flowed they were swept back and 

 forth across the rocks. This may account for some being with- 

 out fronds. The same condition was noticed along the east 

 side of the island and also off Point Caution. The plants next 

 the shore were nearly all frondless. In each of these cases 

 the shore is abrupt. South of Turn Island the shore is gently 

 sloping and the plants there, similarly placed to those in the 

 places just mentioned, were healthy. 



Yet these observations have not accounted for the numbers 

 of bald-heads in the strong currents. Drifting back to the 

 Station after making observation No. 26, the writer's atten- 

 tion was caught by some fronds in the thick clusters west of 

 Shaw Point which had been thrown up over the floating pneu- 

 matocysts of neighboring plants and, exposed to sun and wind, 

 had become discolored and dry. However, they were not crisp 

 enough to break. Yet this suggested a new factor and it was 

 late when the Station was reached. Several like cases were 

 found that evening. The field from below Turn Island to 

 Point Caution was resurveyed with this point in mind and 

 thirty-six similar cases found, all being of plants in the center 

 of thick clumps. Some were so crisp as to break off like dead 

 leaves when handled. Unfortunately, bad weather prevented 

 watching these closely. So in the quiet water near camp a 

 fine healthy plant was selected, exposed to tide currents and 

 the wash from every passing vessel. A rude raft of boards 

 was built about it and the fronds were thrown up over this in 

 the same manner as had been observed in the field. A few 

 were left floating as a check. On account of the wash from 

 vessels it was very difficult to keep them as desired without 

 tying the fronds themselves, which would have introduced a 



