THE THALLOPHYTES 335 
plants of this group. Some of them also possess phycoerythrin, a 
red pigment. Their bodies are usually covered with a gelatinous" 
envelope which may be in layers. In many of them the proto- 
plast is differentiated into a peripheral pigment containing region 
and a central colorless region. The unicellular forms reproduce 
by binary fission while many of the filamentous forms reproduce 
by the separation of one or more segments of the filament from 
the rest of the body which move away and develop into new 
individuals. These segments are called hormogonia. ‘They are 
found everywhere in fresh and salt water and also on damp logs, 
rocks, bark of trees, stone walls, in the roots of Cycads, etc. 
Examples: Oscillatoria, Gleocapsa, Nostoc, Anabena, Rivularia, and 
Spirulina. 
GiaocapsA.—This blue-green alga is commonly found on 
old, damp flower pots in greenhouses and on damp rocks and walls 
near springs, where it forms slimy masses. Under the microscope 
a mount of Gloeocapsa will be seen to consist of isolated proto- 
plasts and groups of protoplasts, surrounded by concentric 
_gelatinous envelopes. Each protoplast consists of a protoplasmic 
mass which contains blue and green pigments. No definitely 
organized nucleus is apparent but chromatin in the form of 
granules is scattered through the protoplasm. The whole is 
surrounded by a cell wall which undergoes mucilaginous modi- 
fication producing thus the soft gelatinous envelopes which 
encircle parent-, daughter-, grand-daughter- and even 
great-grand-daughter-cells. 
OscILLATORIA. —Oscillatoria is a blue-green, filamentous 
organism ‘found abundantly on the surface of the mud of drains 
and ditches as well as in ponds where the water is foul. The 
filament is slender and composed of compactly arranged disc- 
shaped cells which are all alike, excepting the terminal ones 
which appear rounded off. Each filament is surrounded by a 
gelatinous sheath. The filaments tend to be agglomerated in 
thick felts or gelatinous masses and each possesses peculiar 
oscillating and forward creeping movements. At the time of 
reproduction the filament breaks up transversely into short 
segments or hormogonia each of which, by fission occurring 
among its cells, grows into a new filament. 
