The Role of the Terrestrial Alga in Nature 213 



means of atmospheric vapor. Probably the same is also true to a 

 large degree of Trentepohlia (Irgang,** p. 15). 



Note: This essay was completed in July, 1934. Since then Miss James's paper 

 referred to on page 196 has been published (see Beih. bot. Centralbl., 53, A, 519- 

 553, 1935). There has also appeared a detailed study of soil Algae by J. B. Peter- 

 sen (Dansk. Bot. Arkiv, 8, no. 9, 1935) in which the author arrives at conclusions 

 which to a considerable extent agree with those propounded above with respect 

 to the subterranean community. 



