CHLOROPHYCE^ 



(Green Algae) 



THE Green Algas attain their greatest development in fresh water, 

 and the number of known species is exceedingly large (probably about 

 5000). 



The group-name Chlorophycese is here used in its original and proper 

 sense to include all Green Algae. The separation instituted by Wille ('97) 

 into ' Conjugates ' and ' Chlorophycese' is scarcely justified by our knowledge 

 of the structure, life-histories, and probable inter-relationships of the Green 

 Algse ; and the adoption of the name ' Chlorophycese ' by Wille to include 

 merely those Green Algoe other than the Conjugatse is a misuse of the 

 original name. Species of Spirogyra or Desmids are just as much Green 

 Algse as species of (Edoyonium or Selenastrum. 



In no other group of plants are there such wide differences in form and 

 cytological structure, or such varied life-histories as can be found even 

 in one section of the Green Algse. It is this great diversity which makes 

 the group at first so difficult for the student, and it is also the reason why it 

 is impossible to treat of the Green Algse as a whole in the comprehensive 

 way adopted for the three preceding groups. Many forms, including some of 

 the more primitive, are unicellular; some are coenocytic, the whole plant 

 consisting of what may perhaps be regarded as an aggregate of protoplasts 

 within a common cell-wall ; some are incompletely septate, each segment 

 being a coenocyte containing a number of protoplasts, the septation of the 

 plant being quite independent of nuclear divisions; and others are multi- 

 cellular or completely septate, each segment, which is in this case a single 

 cell, containing one protoplast. 



Not only are large numbers of Green Algse unicellular or colonial in 

 habit, but every degree of simple or branched filament is met with in the 

 various groups ; and in some the thalli are flat, almost parenchymatous 

 expansions, or even cushion-like masses of tissue. In some of the Siphonales 

 and Siphonocladiales the interlaced branches of profusely branched coenocy tes 

 give rise to structures resembling the shoots and leaves of higher plants 



