136 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



nies, or any two, or even all three, may occur in the same 

 colony, but in varying proportions ; the antheridia may dis- 

 charge the antherozoids within the mother colony, or may escape 

 intact, and discharge their contents afterwards. The arrange- 

 ment for cross fertilization is specially noticeable ; the oogonia 

 in a colony ripening before the antheridia can be fertilized only 

 by antherozoids from another colony. It is interesting to 

 observe, here in what was a debatable land between animals 

 and plants, as efficient arrangements for cross-fertilization as we 

 find among flowering plants. 



Family 3. TETRASPORACEAE. 



Cells normally imbedded in gelatine, in structure like cells 

 of Chlamydomonas, but usually without cilia ; dividing vegeta- 

 tively ; asexual reproduction by cells assuming 2 or 4 cilia, 

 escaping from the gelatine, and after a relatively long free 

 existence, coming to rest, and producing a normal colony 

 directly or after a Palmella stage ; sexual reproduction by 

 the division of a cell into several zoogametes, by whose copula- 

 tion is formed a zygote, germinating at once or after a resting 

 period. 



KEY TO THE GENERA OF TETRASPORACEAE. 



i. Cells without order in formless gelatine. i. PALMEIXA. 



i. Cells and colony with some definite form and arrangement. 2. 



2. Cells radiately arrangedin a botryoidal mass. 



2. BOTRYOCOCCUS. 



2. Cells not radiately arranged. 3. 



3. Each family enclosed in a tough, elastic membrane. 



3. INEFFIGIATA. 

 3. Membrane, if any, soft and delicate. 4. 



4. Cells borne on filamentous, branching stalks. 5. 



4. Cells without definite stalks. 6. 



5. Frond soft and loose, gelatine not very conspicuous. 



7. PRASINOCLADUS. 

 5. Frond firm, at first solid, later hollow. 8. COHINSIELLA. 



6. Mature frond a hollow sac of definite form. 7. 



6. Mature frond an expanded membrane or long filament. 



4. TETRASPORA. 



7. Sac solitary, pyriform. .5. APIOCYSTIS. 



7. Sacs subcylindrical, united at base. 6. PALMODACTYLON. 



i. PALMELLA Lyngbye, 1819, p. 203. 



Cells spherical, with bell-shaped chromatophore and one pyre- 

 noid, with broad, gelatinous, diffluent membrane; asexual re- 



