252 



Heterokontce 



branched colonies ; they are situated only at the extremities of the 

 mucous tubes and each possesses from one to four chromatophores. 

 Reproduction takes place by zoogonidia and isogamous piano- 

 gametes. The zoogonidia usually germinate directly to form a 

 small typical colony, but the zygospore divides in two directions 

 in one plane forming an epiphytic cushion, all the cells of which 

 are situated on short, broad, mucilaginous stalks. 



Fig. 118. Mischococcus confervicola Nag. A, from Cam Fell, W. Yorks.; 

 B and C, from Ruislip Eeservoir, Middlesex ( x 500). 



M. confervicola Nag. is a rather uncommon Alga, occurring as an epiphyte 

 on various filamentous species of Cladophoracese, Tribonemacete, Ulotrichacete, 

 (Edogoniacese, etc. It is generally found in small ponds and ditches, or more 

 rarely in peaty pools; diam. of cells 3'5 5'5 /*; fig. 118. 



Another genus belonging to the Chlorotheciaceae has been 

 recently described by Schmidle 1 under the name of Oodesmus. 

 Lemmermann reports having found this genus in some plankton 

 material forwarded to him from Loch Doon, Ayrshire. The cells 

 are ovoid and united by short bands of mucus to form free- 

 swimming colonies. Each colony consists of four cells, which are 

 disposed in one plane. The cell-wall is relatively thick and there 

 are one or two chromatophores in each cell. 0. Doederleinii 

 Schmidle is the only known species ; cells 8 p in length and 6 //, in 

 breadth. 



1 Schmidle in Hedwigia, Bd xli, Heft 4, 1902, p. 162, fig. B 4. 



