1915 



Muenscher ; on Scntceeds 



21 



exposure, and whether or not it lived when it was returned to its natural 

 habitat. 



Each species was experimented with until the approximate time of 

 exposure which it could resist was determined. This period of exposure 

 was worked out for thirteen species. These were then arranged in the 

 order of their ability to withstand desiccation {Table 1). The last 

 column gives the number of hours of desiccation which the species can 

 resist, and still live when it is returned to its natural habitat. Individuals 

 of the same species in some cases varied in their ability to resist exposure. 

 This may be due to individual differences in the plants ; but more likely 

 to variations in the amount of humidity in the air, the temperature of the 

 air, or the velocity of the wind. 



Table 1. Showing Ability to Withstand Desiccation. 



The first column of Table 1 contains the names of the species used 

 in the order of their ability to withstand desiccation. The second 

 column gives the number of individuals experimented with of each species. 

 The fourth and fifth columns record the minimum and maximum time 

 during which plants were exposed to the sun. The last column gives 

 the number of hours during which the plants could resist desiccation and 

 still continue to live when returned to the water. 



Fuctis evanescens was hard to spread out evenly so that no branches 

 of the thallus overlapped ; for this reason it was often found that the 

 entire plant did not die at the same time. It was also found that the 

 younger plants could resist desiccation more than the older ones. In no 



