184 
PHARMACEUTICAL BOTANY 
and composed of compactly arranged disc-shaped cells which are 
all alike, excepting the terminal ones which appear rounded off. 
The filaments tend to be agglomerated in thick felts or gelatinous 
masses and each possesses peculiar oscil- 
lating and forward movements. At the 
time of reproduction the filament breaks 
up transversely into short segments, each 
of which, by fission occurring among its 
cells, grows into a new filament. 
Nostoc. — Nos toe occurs on the damp 
ground bordering streams or in slow 
bodies of water as greenish or brownish 
tough gelatinous masses varying in size 
from a pea to a hen’s egg. When one of 
these masses is dissected and examined 
microscopically, it is seen to contain, im- 
bedded in a gelatinous matrix, numerous 
serpentine filaments, composed of spherical 
or elliptical cells loosely attached to each 
other in chain-like fashion. Most of the 
cells are of the blue-green vegetative kind 
but there occur at intervals larger cells, 
often devoid of protoplasm which are 
termed heterocysts. Frequently the fila- 
ments break apart on either side of the 
heterocyst, setting free segments of cells 
which grow into new filaments. 
SUBDIVISION II— MYXOMYCETES, OR 
SLIME MOLDS 
Terrestrial or aquatic organisms, fre- 
quently classified as belonging to the 
animal kingdom and found commonly on 
decaying wood, leaves, or humous soil in 
forests. Their vegetative body consists of a naked, multinucleated 
mass of protoplasm called the plasmodium, which has a creeping 
and rolling amoeboid motion, putting out and retracting regions 
Fig. 74. — Nostoc. 
heterocyst. 
(h). a 
