9 * 
Classification of Green Alga. 
16 . Dactylothece. Lagerheim, 1883. 
Cells oval, straight, or curved, grouped 1-4 in a linear 
series often embedded in mucilage. Division in one 
direction only. 
17. Dimorphococcus. A. Braun, 1849. 
Cells 2-8 in the coenobium, all similar and reniform, or 
the internal ones oval and the external semi-lunar; 
usually arranged in a zigzag line. 
18. Scenedesmus . Meyen, 1829. 
Coenobium of 2-8 (usually 4) cells in one or rarely two 
rows, with rounded or pointed ends. Some or all of 
the cells may bear mucilaginous processes, often 
curved. Chromatophore filling most of the cell. 
Cells known to be capable of living singly in media 
rich in oxygen. 
Series E. Cells more various in form, but often flattened, and 
always united in fours to form plate-like ccenobia or syncoenobia. 
19. Tetrastrum. Chodat, 1895. 
Cells flattened pyramidal with rounded corners, grouped 
in fours, with apices inwards and spines on the 
external face. 
20. Hof mania. Chodat, T900. 
Cells oval, each with a tapering bract-like mucilaginous 
appendage derived from the mother-cell-wall. 
21. Lemmermannia. Chodat, 1899. 
Cells flat, triangular, united by their edges in fours to 
form a square plate. On multiplication the daughter- 
ccenobia remain closely united. 
22. Actinastrum. Lagerheim, 1882. 
Cells elongated-oval or cylindrical, usually cohering by 
their ends to form flat radiating groups of four. 
Arrangement often irregular. 
23. Crucigenia. Morren, 1830. 
Cells of various flattened forms, united directly or by 
processes to form a flat plate with a central perfora¬ 
tion. The ccenobia are usually grouped into 
syncoenobia with some regularity. Daughter-ccenobia 
arise by division of the cell contents cross-wise. 
24. Willea. Schmidle, 1900. 
Characters of Crucigenia , but forming an irregular plate 
of several hundred cells. No pyrenoid. 
25. Crucigeniella. Lemmermann, 1900. 
Cells in fours as in Crucigenia , but without pyrenoids. 
The cells divide only in the plane of the colony and 
the two apposed four-celled colonies thus produced 
soon separate. 
