PETERS: CAUSES THAT PRODUCE "BALD-HEADED" KELP. 5 



With this in mind an inspection of the map shows the heav- 

 iest growth of kelp along the edges of the strongest currents, 

 a fact already discussed by Frye, Setchell, Rigg, and others. 

 The conditions for its growth do not belong here and have 

 been already discussed by Professor Rigg. 1 But the currents 

 play too important a part in this problem to be left unnoticed. 



The bald-headed kelps which were under observation had 

 lost part or all of their fronds. Usually there was a stump 

 left of each which showed a whitened, slimy, apparently half- 

 putrid end. (Fig. 1.) Relieved of the pull of the fronds the floats 

 stood upright several inches out of the water, in sharp contrast 

 to their healthy neighbors. (Fig. 2.) In many cases the side of 

 the bulb had become flattened and wrinkled, in some cases 

 decaying. The flattened, decaying condition was noticed in 

 healthy plants as well, however. In the case of the latter, i. e., 

 those with a full set of fronds, this may be the result of me- 

 chanical injury, but the writer is inclined to think it due to 

 sunburn resulting from a few hours' drying when held out of 

 the water by neighboring plants. With the "bald-heads" it 

 is an indication of the death of the plant, since it soon dies 

 after losing its fronds, as proven by Zeller's experiments in 

 1911.- 



The first thing to attract attention when the observations 

 were begun was the snails, Lacuna sp., present in large num- 

 bers upon many plants. The eggs were laid in jelly-like cap- 

 sules, usually upon the bulb of the pneumatocyst or the bases 

 of the fronds. The writer found them upon all parts of the 

 plant, however, in one case a capsule upon the hapteres pulled 

 from a depth of 39 feet. But the favorite location is as in- 

 dicated above. (Fig. 3.) In feeding the snails eat the epi- 

 dermis and perhaps the first cell layers beneath. As the 

 meristem region is youngest and presumably tenderest, or per- 

 haps because it is exposed to the air, it is the region most fre- 

 quently chosen for a meal. Doctor SetchelP says, "The central 

 or medullary tissues are made up, as a rule, of elongated — 

 often tubular — cells and have for their function the conduction 

 of substances manufactured and distributed from the outer 



1. Professor Riga', Bui. P. S. Marine Sta. Notes on the Ecology and Economic Im- 

 portance of Nereocystia luetkeana. 



2. Professor Riga - , Fertilizer Resources of the U. S., Appendix L, 



3. Doctor Setchell, same, Appendix K. 



