216 ESSENTIALS OF BOTANY 
OSCILLATORIA, — ONE OF THE BLUE-GREEN ALGAE 
273. Occurrence. — Oscillatoria may occur floating in 
stagnant water, about watering troughs or outlets of drains 
and sewers, or on pots in greenhouses. In general it flour- 
ishes in the presence of dissolved and decaying organic 
matter. 
274. Gross Structure. — Examine with the magnifying glass a bit 
taken from a growing mass of the plant and left for some hours in 
a white saucer with a little water. Note: 
(a) The color. 
(0) The filaments radiating from the 
rather compact mass of the plants. 
275. Minute Structure. — With m.p. 
note: 
(a) The shape of the filaments. Are 
they branched ? 
(b) Their movements. Describe these. 
Sketch several filaments. 
Fic. 150. Gleocapsa, one With Dips notes : 
of the Lowest of the Blue- (c) The shape of the tip of a filament. 
Green Algw. (x 300.) (d) The coin-shaped cells of which the 
‘ : filaments are made up. 
A-E, successive stages in the Bee 
development of new indi- (e) The occasional occurrence of a dead 
viduals from a parent-cell. cell, leaving a transparent place in the 
filament. 
(/) The delicate sheath inclosing the filament (best seen where 
a dead cell occurs). Make a careful drawing showing the points 
(¢, d, e, f) above mentioned. 
276. Discussion. — Oscillatoria is a plant of very low 
organization, marked, for example, by the absence of a 
well-defined nucleus in the unit cells of which the fila- 
ments are composed. Each cell is an individual plant, 
although, as the student has seen for himself, they live in 
communities. The flattened form of the cells is evidently 
