92 TUFTS COLLEGE STUDIES, VOL. II, No. 



Class I. HETEROKONTAE. 



Motile cells with two cilia of unequal length ; chromatophore 

 more or less distinctly yellow green ; reserve material oil, not 

 starch ; no pyrenoids. 



Under this name are included by Oltmanns and others, the 

 family Chloromonadaceae of the Flagellates, with genera of 

 algae supposed to be derived from it ; in distinction from the 

 great body of green algae, whose descent is from other forms of 

 Flagellates ; the name is based on the unequal length of the 

 two cilia, one of the two being sometimes quite imperceptible ; 

 though the distinction may appear somewhat artificial, it seems 

 to cover a distinct line of descent and development. Only one 

 order of algae. 



Order CONFERVALES. 



KEY TO THE FAMILIES OF CONFERVALES. 



i. Terrestrial; cell vesicular, with branching underground prolonga- 

 tions. 2. BOTRYDIACEAE. 

 i. Chiefly aquatic ; filamentous or unicellular, without branching pro- 

 longations. 2. 

 2. Unicellular; cells free or connected by gelatinous strands ; sexual 



reproduction by gametes. 3. CHLOROTHECIACEAE. 



2. Unicellular or filamentous ; cell wall with little cellulose ; sexual 

 reproduction unknown. i. CONFERVACEAE. 



Family I. CONFERVACEAE. 



Cells free or united in attached or free monosiphonous fila- 

 ments ; cell wall with little cellulose, mostly pectin ; chromato- 

 phores usually many, disk-shaped, always without pyrenoid, 

 cells containing more or less oily matter but no starch, one or 

 more nuclei ; asexual reproduction by zoospores with two cilia 

 of unequal length, or by aplanospores which often seem to take 

 the place of zoospores under certain conditions of environment ; 

 all plants of fresh water. 



The Confervaceae, as here limited, include genera that have 

 been placed at widely different points in the series of green 

 algae, and their association here is by no means free from ques- 

 tions ; some of them have been reported as having two cilia of 

 equal length, some as having only one ; but these reports may 

 be due to imperfect observations. In most of the genera there 

 is a peculiar stratified arrangement of the cell wall, by which the 



