Glaucocyxtacece 317 



Family 1. GLAUCOCYSTACE^E. 



This family includes four genera, only two of which are known 

 from the British Islands. The plants are unicellular or colonial, 

 and propagation takes place by the division of the cells in one 

 direction only, or by division into two, four, or eight cells after a 

 corresponding division of the nucleus. 



Genus Glaucocystis Itzigsohn, 1854. The cells are ellipsoidal, 

 rarely solitary, but more often occurring in twos, fours, or eights 

 within the enlarged wall of the mother-cell. In external features 

 the plants greatly resemble those of the genus Oocystis, but the 

 chromatophores are central (or axile), and of a bright blue-green 

 colour. Each chromatophore consists of a central mass with from 

 10 20 prolongations, which are more or less radiating and con- 

 siderably curved. 



G. Nostochinearum Itzigsh. is widely distributed throughout the British 

 Islands, but it is somewhat scarce. It is found chiefly among submerged 

 Sphagnum. Length of cells 13 19 p.. 



Genus Chroothece Hansgirg, 1884. The cells are ellipsoidal 

 with a stout enveloping wall, which increases greatly in thickness 

 at one pole, and is conspicuously lamellose. The chromatophore is 

 central with radial outgrowths. 



Ch. Richterianum Hansg. is known from salt marshes in Bohemia, and a 

 small form of it (possibly another species) has been observed on wet limestone 

 rocks in W. Yorkshire. Length of cells (of British form) 20 24 p.. 



Sub-class 2. ARCHIPLASTIDE^:. 



The great majority of the blue-green Algae are included in this 

 sub-class. The plants are unicellular, colonial, or filamentous, and 

 in some of the latter (e.g. Stif/onema, Anabcena, etc.), there is a 

 direct protoplasmic continuity between the cells. The protoplasmic 

 unit in each cell is of a lower type than in any other of the Algse, 

 and has been termed by Nadson 1 an ' archiplast.' The nucleus is 

 of a primitive type, of peculiar form, and without nucleolus 01 

 nuclear membrane ; in consequence of the latter character it has 

 been termed by Hieronymus an ' open nucleus.' The chroma- 

 tophores are likewise of an archaic type, the pigmented protoplasm 

 being scarcely differentiated and never of any characteristic form. 



1 Nadson in Scripta Botanica Horti Univers. Imp. Petropolit. 1895, iv, fasc. 2. 



