Class 6. MYXOPHYCE^] (or Cyanophycese). 



THE Myxophyceae (or Blue-green Algae) is the most primitive 

 class of the Algae, some of the lowest forms having considerable 

 resemblance to the Bacteria. They are often termed the Cyano- 

 phycese 1 , but the earlier name ' Myxophycese ' was given a definite 

 and restricted meaning by Stizenberger, so as to include all those 

 plants now recognized as the blue-green Algae. (Consult Introduc- 

 tion, page 3.) It also emphasizes the most conspicuous habit of 

 these plants, namely, the manner in which the great majority of 

 them exist in gelatinous masses or strata. A few of them are 

 unicellular, some are colonial, and others filamentous. They are 

 found everywhere in damp and wet situations, and many of them 

 are almost entirely subaerial in habit. In moist climates many of 

 the richest tints of the landscape are due to the presence of Algse 

 of this class, which occur in every conceivable situation on rocks, 

 stones, and the trunks of trees, and in some regions they give 

 a decided character to the country 2 . The filamentous species 

 frequently form compact, felt-like, mucous or leathery patches of 

 various colours and of considerable extent, occurring on the vertical 

 faces of rocks which are kept permanently moist or wet. Numerous 

 Myxophyceae occur in the sea, although they are more abundant in 

 fresh water. Many of them exist in quantity in both the marine 

 and freshwater plankton. 



Some of the Myxophyceae have become adapted to a life in hot 

 water, and they constitute the principal vegetation of hot-springs. 

 The part played by certain of these Algae in the formation of rock- 



1 There was little necessity for the re-naming of this class by either Rabenhorst 

 (who termed it the Phycochromophyceffi) or Sachs (who termed it the Cyanophycese). 

 The class already possessed much the best name that has yet been given it (the 

 Myxophycese), and the exactitude of its limitations could not be improved upon 

 by either of those authors. 



2 The Pedras negra.8 of Angola are due to the prolific growth of Scytonema 

 Myoclirom var. chorographicum ; vide West& G. S. West in Jourii. Bot. 1897, p. 303. 



