1915 Muenscher; on Seaweeds 23 



is dry it is dark green and brittle, but it soon looses its color and decays 

 when it is returned to the water after more than two hours of desiccation. 



Nereocystis luetkeana, the largest species experimented with, has a 

 long stipe, holdfast, bulb, and blades. The blades are very sensitive to 

 drying and can stand from one to two hours depending upon the size of 

 rhe blade and the weather conditions. When whole plants were exposed 

 for more than two hours they were very dry. When these were returned 

 to the water they turned green, and soon the blades, bulb and stipe 

 decayed. 



Sarcophyllis californica can stand less than one hour of drying. Al- 

 most immediately after it is removed from the water it turns from red 

 to a bright orange ; when it is then returned to the water it looses its 

 color and decays. 



Desmarestia acideata turns green within one hour after it is re- 

 moved from the water. In no case did a plant live after it had been ex- 

 posed to the sun for one hour or more. 



Alaria valida is very sensitive to drying. In no case did a plant live 

 after it had been dried for one hour. The plant dries out quickly ; then 

 Avhen returned to the water it turns green and permanently looses its 

 turgidity. 



The observations were limited and made under somewhat variable 

 conditions, but th€ general results are valuable in that they open the 

 way for both intensive and extensive work along this line. The ex- 

 periments show that some plants can live after they have been exposed 

 to the sun for two days ; others can resist exposure for only one tide ; still 

 others are practically doomed to die if they are taken from the water 

 for an hour or less, and thus, if washed ashore and left until the tide 

 comes in again they are sure to die. 



The table shows that those plants which grow liighest above the 

 low tide line can stand the most desiccation and those species which 

 grow at or near the low tide line can stand the least desiccation. In the 

 distribution of seaweeds above the low tide line wave action is not as 

 much a factor as the ability to withstand desiccation, because those plants 

 growing at or near the low tide line are subject to the beating of the 

 waves when the tide is low as well as those growing higher up along the 

 shore. While it is not claimed that the ability to withstand desiccation 

 is the only reason why some algae grow high above the low tide line the 

 data shows conclusively that drought is one of the causes why certain 

 seaweeds do not grow much above the low tide line. 



