. SCHIZOPHYTA 



Oscillatoria is a filamentous type, which is common on damp walU 

 and rocks. Its pale green filaments show slow swin-j 

 hence the name (Fig. 390). They consist of di 

 which multiply by division. In some of the larger forms' granules 

 of irregular form are found in each cell, giving the staining re- 

 actions of chromatin, and dividing before division of the cd! b-.r 

 without a definite nuclear spindle. The filaments may brea), 

 any point into shorter lengths, and are unattached. In oth.:r . .»-rs 

 special cells (heterocysts) occur at intervals in the filaments, which 

 appear to determine their breaking up into shorter length^'. 



l-7i.VV- 



m 



Fig. 390. 



A , Oscillatoria prhiceps : a terminal portion of a filament ; b, portions from the 

 middle of a filament, properly fixed and stained ; /, cells in division. ( k ioSo;. 



B, Oscillatoria Froclichii. ( x 540). S. 



Nostoc or Rivularia. Some of these fission-Algae take part in the 

 formation of Lichens : thus Collema has Nostoc as its Algal constituent. 

 Others, such as Anabaena, lead an endophytic life, contributing 

 probably to an irregular nutrition, as in the roots of Cycads. In the 

 establishment of the new Flora of the sterilised Island of Krakatoa 

 (p. 295), blue-green Algae were among the first colonists, t " r 



part in the preparation of an organic soil for larger dc\ 

 to follow. Certain of these Algae allied to Anabaena often appear 

 suddenly in large quantities on the surface of fresh water, causing the 

 phenomenon known as " water bloom," or the '* breaking of the 

 meres." One of these, with a deep red colour (Truhodt.smiuv: 

 thraeum), floats in ocean-waters, and becomes prominent when n. 

 together by wind and tidal streams. It has thus attracted-att. 

 in various oceans, and has given its name to the " Red Sea," 



