SUB-CLASS IT 
CHLOROPHYCE 
THE Chlorophycew attain their finest development 
in fresh waters, but representatives of most of the 
orders occur in the sea. The multicellular forms 
never attain a higher stage of development than 
branched or simple cell-rows or flat expanses of 
indefinite form. The unicellular forms, however, in 
addition to the simple Algze usually so called, are 
represented by the multinucleate orders in which the 
highly developed thallus is a conspicuous feature. 
Oogamous reproduction occurs here, as in the 
Pheeophycee, but mostly in fresh-water forms. It is 
represented in the sea in the marine species of 
Vaucheria only, and this type of oogamous reproduc- 
tion differs from that of Phaophycew (Fucacee) in 
respect of the fact that the fertilised oosphere is not 
extruded but remains i sité in the parent plant. 
The fact of the occurrence of this high type of 
reproduction almost exclusively in fresh-water forms, 
and in those Algse with chromatophores most nearly 
resembling terrestrial vegetation, points to this group 
