316 Myxophycece 



Algae concerned in these phenomena are generally species which 

 normally occur in the plankton of lakes and rivers. The extra- 

 ordinary rapidity of their increase and the consequent discolour- 

 ation of the water, together with their equally rapid disappearance, 

 constitute one of the most remarkable facts in the whole domain 

 of algological inquiry. Nelson 1 finds that the presence of this 

 ' water-bloom ' often has a fatal effect on cattle which have been 

 drinking the water 2 . 



The Myxophycea3, regarded as a whole, are unquestionably of 

 a lower type of organisation than any other class of Algae, and 

 they must be looked upon as an archaic group which is very little 

 in advance of the Schizomycetes (or Bacteria). 



The group of the Glaucocystideae is much in advance of the rest 

 of the blue-green Algae, the cells possessing a highly specialised 

 chromatophore and a more highly organised nucleus. This necessi- 

 tates a primary subdivision of the class into two sub-classes, the 

 Glaucocystideae and the Archiplastideae. 



Sub-class 1. Glaucocystidece. Cells with a distinct and highly 

 differentiated chromatophdre, and with a true 

 cell-nucleus. 



Sub-class 2. Archiplastidece. Cells with a lower type of 

 chromatophore, often scarcely differentiated, and 

 with a primitive type of nucleus. 



Sub-class 1. GLAUCOCYSTIDEAE. 



This sub-class has been instituted in order to include a few 

 blue-green Algae which are sharply demarcated from the rest of 

 the Myxophyceae by their cytological structure. There is a true 

 cell-nucleus and also a highly differentiated chromatophore, 

 both of these characters being a distinct advance on all other 

 Myxophyceae. 



1 N. P. B. Nelson in Minnesota Bot. Studies, 1903, iii, pp. 4750. 



2 Other blue-green Algae also appear to be poisonous. Mr Herbert Wright has 

 forwarded me specimens of Lyngbya majuscula Harvey from coral beaches in the 

 Gulf of Mannar, where it occurs in abundance; and he states that numbers of 

 horses have frequently been killed by feeding on it. 



