51 



the water, the level of which is perpetually changing, and the 

 pulling action of the ebb and flow of the tide cause the free end 

 to tug at the holdfast like a ship at anchor. 



A few summers ago I wished to put up material of the " fruit " 

 of Nereocystis for microscopical examination and for the pur- 

 pose it was necessary to obtain fresh sporophylls. I found a 

 place near the Hopkins Seaside Laboratory where the plants grew 

 in abundance. They were out of reach from the shore by hand 

 but I found that they could be reached with a long-handled gaff- 

 hook. The attempt was made at first to pull from the water the 

 smallest by placing the hook back of the bladder, but I was un- 

 able to get any plants in this manner. Next the hook was used 

 as a hatchet in the hope that some of the leaves might be torn 

 away, but they were so tough and smooth that this also failed. 

 Finally, I tried to tear the cyst in two by striking the sharp hooks 

 into it ; much to my surprise the large bladders cracked across 

 like the most fragile substance. I tried repeatedly blows of vary- 

 ing force and found that even a slight one was sufficient to break 

 either the cyst or the stem. Through this unexpected weakness 

 of the plant I had no difficulty in obtaining all of the sporophylls 

 that were desired. It should be said that the plant loses this 

 brittle character when it is exposed to the air. 



In seeking for a cause of this mechanical weakness of the stem 

 of the bladder kelp, i. e., to its inability to withstand the stresses 

 to which I subjected it, it occurred to me to compare the habitat 

 of another form, as for instance the sea palm, with that of the 

 bladder kelp and also the mechanical strength of the former with 

 that of the latter. The sea palm was chosen because its habitat 

 and habit are well marked and quite different from that of the 

 bladder kelp. These will be considered very briefly. 



The sea palm is usually about two feet high. Like the blad- 

 der kelp, it has a holdfast, a stem, and a crown of leaves or 

 sporophylls. The stem is upright and quite independent of sup- 

 port from the water. The plant grows on sloping rocks between 

 tide marks. The position of the sea palm is such that it is 

 pounded with inconceivable force by the waves in the times of 

 high seas, and always when the tide is in, it is subject to the 



