THE ALG 67 
General study.—On the shady side of trees, rocks, and 
fences in rather damp places this plant may be seen as a 
slimy growth, which when quite damp is bright green, and is 
grayish or brown as the amount of moisture is diminished. 
Any group which may be recognized probably contains many 
thousand individual plants. A piece of bark on which these 
are growing will be suitable for laboratory study. 
Vegetative or growing structures.—Examine the mass 
of plants with the hand lens. Can you see anything more 
than a green coating upon the bark? Any separate plant- 
cells? By using the scalpel remove a small amount of the 
green mass, place it in a drop of water on the slide, spread 
it thoroughly, place on the cover-slip, and examine with the 
low power of the microscope. ; 
Distinguish between the fragments of the bark and the 
small cells, each of which is one Plewrococcus plant. Do the 
plants tend to group themselves? What is the form of a 
single plant? 
Select a region on the slide where the material is favor- 
able for study, adjust the high power, and study carefully 
the structure of the plant. Note (a) the cell-wall, its color 
and form; (b) the protoplasm, most of which is obscured by 
the green coloring-matter known as chlorophyll. Is the 
chlorophyll contained in definite plastids, as was true in the 
cell from the moss leaf previously examined? Can you see 
any of the cytoplasm where it is not obscured by the chloro- 
phyll? Usually the cell-nucleus can not be seen in fresh 
Pleurococcus plants. It may sometimes be seen after a small 
amount of an iodin solution has been added to the mount. 
Make an accurate drawing of one or two plants, exaggerat- 
ing considerably the natural size. 
Reproduction.—Look over the mount carefully and de- 
termine how Pleurococcus reproduces itself. How many 
stages in the process can be found? When one plant has 
formed two new ones, do the new ones always become free 
