84 



are probabl}' concerned with water storage. How far the absorp- 

 tion of atmospheric moisture from fog takes place during the dry 

 season has not been tested, but to judge from the behavior of 

 the lichens of this region, shown by Professor Peirce's experi- 

 ments, it may well be considerable. 



The development of tubers has been observed by various stu- 

 dents of liverworts.* A very perfect case is that of the re- 

 markable liverwort, Geothalliis, discovered some years ago by the 

 writer. This liverwort comes from southern California, where 

 the rainfall is much less than in middle California. In this spe- 

 cies the inner tissue of the thallus becomes filled with reserve 

 food, and the surrounding cells become dark and thick-walled, 

 forming a sort of rind protecting the central tissue. These tubers 

 are more or less completely buried in the earth, where they re- 

 main during the long dry season. Only a very small amount of 

 tissue about the growing point remains alive, and no signs of 

 the young reproductive organs are visible when the tubers begin 

 to germinate. A similar condition, but much less pronounced, 

 is sometimes found in Fossovibronia, this being decidedly more 

 marked in specimens from the southern part of the state. 



Goebelf mentions the formation of tubers in several species 

 oi Antlioceros, and they have also been observed in some Cali- 

 fornian species.! The thallus oi Antlioceros develops an unusual 

 amount of mucilage within its tissues, and this undoubtedly is 

 an important factor in their survival of the dry season. Whether 

 the association of colonies of Nostoc, which always are present, 

 is of service in water storage has not been determined ; but it is 

 by no means unlikely. 



Some of the Californian pteridophytes behave much as do the 

 liverworts. Such species of Sclai^inclla, as 5. Bigclovii, and 5. 

 Icf^idopJiylla, dry up during the greater part of the year, but 

 absorb water through their leaves, and resume the active condi- 

 tion very promptly. The latter species is the " rcsurrection- 



* See Howe, Hepatic;o and .Anlhoccrotes of California, Mem. Torrey Club, 7 : 69. 

 1899. 



t Organographie (ler I'flanzcn. /.weitcr Tlicil. Heft. I, p. 293. 

 X Howe, /. c. 



