232 Chlorophycece 



are so deep that there is no central body. C. rhaphidioides Reinsch 

 and C. longispina (Perty) W. & G. S. West are both plants of 

 rare occurrence. 



Sub-family VI. PHYTHELIE^. 



This is one of the most interesting sub-families of the Pro- 

 tococcacese, and the Alga? contained in it have only recently been 

 brought to light, largely by the plankton investigations of 

 Lemmermann and Chodat. The plants are unicellular or some- 

 times grouped so as to form a more or less definite coenobium, 

 and in all cases they float freely in the water. As a rule the cells 

 are almost devoid of a mucous envelope, and they are furnished 

 with several stiff bristles considerably longer than their own 

 diameter. Multiplication occurs typically by the formation of 

 autospores, which usually attain all the characters of the adult 

 before their liberation from the swollen wall of the mother-cell. 

 Zoogonidia have been observed in Golenkinia. 



The name of the sub-family is derived from the genus Phythelios 

 Frenzel (1891), an Alga which was originally described as a 

 Heliozoan. All the genera are practically confined to the plankton 

 of large lakes, although a few of them are occasionally observed in 

 the surface waters of ponds. The long bristles of these Algae are 

 protective characters developed as a result of a free-floating 

 existence amidst numerous animals to which they would other- 

 wise be an easy prey. 



The genera have been well worked out and monographed by 

 Lemmermann 1 . Four of them are known from Britain. 



A. Cells globular. 



* Cells solitary with evenly distributed bristles Golenkinia, 



** Cells in colonies of 8, 16, or more, bristles attached 



to the outer faces only Richteriella. 



B. Cells ellipsoid or subcylindrical. 



* Bristles with a basal swelling Lagerheimia. 



** Bristles without a basal swelling Chodatella. 



Genus Golenkinia Chodat, 1894. The cells are globular, 

 usually solitary, with a firm cellulose wall, which is enveloped in a 

 thin layer of mucilage. Each cell is furnished with a number of 

 radiating bristles of considerable length, evenly disposed over the 



1 Lemmermann in Hedwigia, Bd xxxvii, 1898. 



