THE GREEN ALG^ 



483 



ments instead of being distinct grow together into a mass 

 by the coalescence of adjacent cells. ^Slany of the cells 

 produce hair-hke outgrowths, and they are all uninucleate. 



Any of the cells maj' form a single swarm-spore like that shown 

 in Fig. 315 D, which, as will be noticed, has but two flagella. Such a 

 spore, after attaching itself to some support, divides into a cell-row 



Fig. 314. — Free-branching Sheath-alga {Coleochcete soluta. Sheath-alga 

 Family, Coleochcetacece) . A, plant sho^\-ing flat system of branching, 

 and bristle-like outgrowths (/i), ■^i'^- 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 se.xual reproduc- 

 tion takes place as follows. The protoplasts of certain smaU 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. 



