16 PLANT MORPHOLOGY 



that the earliest forms of life may have been similarly undifferentiated 

 and that from such a common ancestry both plants and animals may have 

 arisen. Although the relationship of the Cyanophyceae to the flagellates, 

 if any, is very obscure, most of the higher algal groups are thought to have 

 been derived from flagellate ancestors. Where intermediate forms occur, 

 such a derivation seems almost certain. 



Summary. The Eugienophyceae are a group of flagellates with 

 bright green chloroplasts containing only chlorophyll and its associated 

 carotinoids, the chlorophyll predominating, as in the green algae. Some 

 members are colorless, these being either saprophytic or animal-like 

 in their nutrition. All are unicellular and uninucleate, the cells being 

 solitary or rarely in colonies. The cells have one or two cilia (flagella) 

 that may be equal or unequal but are always attached anteriorly. Except 

 in colonial forms, the cells are motile and lack a cell wall. Reserve food is 

 stored as paramylon and often also as oil. Reproduction occurs by 

 longitudinal fission. Resting cells (cysts) are commonly formed. Sexual 

 reproduction is doubtful. 



3. CHRYSOPHYCEAE 



The Chrysophyceae, or golden-brown algae, are a small group number- 

 ing only about 200 species and occurring mainly in fresh water. Their 

 plastids contain chlorophyll and an excess of yellow and brown carotinoid 

 pigments, giving them a golden-brown color. Most members are flagel- 

 lates, being unicellular motile forms without a cell wall. The cells are 

 solitary or in colonies and may be either free-swimming or attached. 

 Motile cells have one or two, rarely three, cilia (flagella) attached anteri- 

 orly. The two cilia may be equal or unequal in length. A few forms 

 have a cell wall and are either filamentous or palmelloid, the latter with 

 cells loosely held together in a gelatinous matrix. All members are 

 uninucleate. Food is stored as oil or as leucosin, which is a protein-like 

 substance of unknown composition. Some forms are colorless, while 

 a few, with chlorophyll, may ingest soUd food. Reproduction occurs by 

 fission, mainly longitudinal. A characteristic feature is the occurrence of 

 cysts with a silicified cell wall having a small plug at one end. Zoospores 

 may be produced in members that are not flagellates. Sexual repro- 

 duction is of doubtful occurrence. 



Chromulina is a motile unicellular form (Fig. 6). Chrysamoeba is 

 amoeboid. Symira and Uroglena are globular free-swimming colonies. 

 Dinobryon has species in which the cells form a dendroid colony. Hydru- 

 rus and Phaeocystis are palmelloid forms. Phaeothamnion is a branched 

 filament and represents the highest type of organization attained by the 

 group. 



