672 Our Fresh- Water Alge. 
enceof a beautiful blue coloring matter, phycocyan ; and for the fact 
that no sexual modes of propagation have been discovered in them; 
nor, at least with rare exceptions, is there any evident nucleus, or 
central denser protoplasmic body, in their cells, such as is the rule 
elsewhere among plants. 
Multiplication in the algæ takes place in either of several ways; 
the most common is that of fission, as in the multiplication of cells 
in a flowering-plant, where each cell divides into two parts, each a 
perfect whole like its parent. The two parts gradually increase in 
size until they reach their full degree, then themselves divide again, — 
and soon. They may or may not remain attached to each other. 
Another mode of algal multiplication is by budding (gemmation), 
where the bud-like protrusion which grows into a new cell remains 
usually attached to its parent. A modification of this, prolification, 
consists of numbers of new cells arising from the side or end of the 
old, as if intended to become a separate individual, but often long 
adhering to the other, as if an attached child unwilling to remove 
from its parent. Some alge, as the Caulerpa, rely on this method 
for their chief mode of propagation, as do so many of the higher 
plants upon “ spreading by the root ” in place of production of seed. 
Another curious modification of budding is common in the red 
algee, the production of tetraspores, bodies which are formed by 
division of a cell into four equal parts, each of which becomes a 
spore, able to grow into a new plant, and thus analogous to the 
bulblets produced by tiger-lilies and some onions. 
Other algæ are reproduced by sexual methods, producing spores 
in some part of the process. Among the most remarkable of these 
are the zoospores, small seed-like bodies, usually soft and oval, 
sometimes spherical, tipped with one, two or more waving t 
(cilia), which lash the water and carry the spore onward in the 
current thus produced, sometimes with great velocity and sometime 
for several hours. The cilia finally fall off and the zoospore comes 
to rest ; and if favorable conditions have befallen it, it has effec 
a lodgement on some resisting substance, there to begin to lengthen, 
divide into cells, and grow into a new plant. During their m e 
stage these little spores seem like so many little green animalcu!es 
darting about ; so indeed they were long thought to be; and P 
names still perpetuates this idea, the word zoospore meanmg 
“ animal-spore.” 
