THE GREEN ALG 483 
ments instead of being distinct grow together into a mass 
by the coalescence of adjacent cells. Many of the cells 
produce hair-like outgrowths, and they are all uninucleate. 
Any of the cells may form a single swarm-spore like that shown 
in Fig. 315 D, which, as will be noticed, has but two flagella. Sucha 
spore, after attaching itself to some support, divides into a cell-row 
Fic. 314.—¥ree-branching Sheath-alga (Coleochete soluta, Sheath-alga 
Family, Coleochetacee). A, plant showing flat system of branching, 
and bristle-like outgrowths (h), 172. B, part of disk, further enlarged; 
a-g show successive stages in the branching of terminal cells. (Pring- 
sheim.)—Thallus forming bright green spots on plants or other sub- 
merged objects in fresh water, in Europe and America. 
which by further division becomes a mature thallus. Besides this 
non-sexual method of propagation a well-marked sexual reproduc- 
tion takes place as follows. The protoplasts of certain small usually 
terminal cells (an, Fig. 315, A) become transformed into flagellate 
bodies like the swarm-spores only smaller (z); while other terminal 
cells (og, Fig. 315, A) enlarge, become flask-shaped by the formation 
of a long neck opening at the top, and finally contract the protoplast 
into a sphere at the base. The motile body as soon as it is set free 
swims to the flask-cell, enters the opening, forces its way down the 
neck to the large protoplast, and fuses with it. 
