HENRIK PRINTZ ■ ; '* [1920 



and with grealer certainty, at least if they are examined at various 

 times. 



Another feature of general biological initerest I will point out, 

 viz. that the subaérlal algae form natura! plant-communities. The 

 various species do not occur s.pread around, mixed arbitrarily, but 

 species with the siame demands on their environments unite in 

 natural plant-communities. I have thus noticed that PhijsoUnunx 

 inonile primarily occurs associiated with certain liver-mosses, 

 partly also with Trentepohlia aiirea; associated with species of 

 ProtococcLis is usually found Acanthococciis, etc. However, it must 

 be remembered that tliis interdependence, as far as less known and 

 less investigated species are concerned, may indioate a genetic 

 affinity. On_ piants with a smooth and hard trunk, e. g. bamboo, 

 it is only a few species that are able to find hold, and here usually 

 only occur piants that have an adhesive growth, e. g. Phijcopeltis 

 nrundinacea, and some others, a flora very different from the one 

 found on rugged bark. However, my material is too scanty and 

 accidental and wanting the necessary information about the nature 

 of the habitat for making further conclusions from it. 



In the foUowing account I have for each species put down the 

 number of all the samples, wherein the alga concerned has been 

 observed. This I consider as not being without interest, as it gives 

 an idea of the relative frequency of the different species. 



