CHAPTER XV 
CHLOROPHYCEAE. GREEN ALGAE 
For experiments in most phases of botanical microtechnic, no 
group of plants affords better material than the green algae, since the 
killing, fixing, and staining can be watched directly; the effect of 
the change from one solution to another can be observed; and even 
the behavior during infiltration with paraffin can be determined with 
considerable accuracy. 
Since the Chlorophyceae furnish our best illustrations of the 
evolution of the plant body, the origin and development of sex, and 
also the beginning of alternation of generations, they occupy a 
prominent place in any well-planned course in the morphology of 
plants; and, if they were better known, the ease with which the 
reactions of the individual cell may be observed would make them 
valuable to the physiologist. 
They are found in both fresh and salt water, but are most abun¬ 
dant in fresh water. The ponds, ditches, and rivers of any locality 
will yield an abundance and variety both of the unicellular and the 
multicellular members of this group. Most of the forms are inde¬ 
pendent, but there are epiphytic, endophytic, and saprophytic 
species. The larger forms and those which grow in tufts or mats are 
readily recognized in the field. Many of the smaller forms are 
attached to other water plants. Drain the water plants and then 
squeeze them over a bottle. The sediment is likely to contain a 
variety of unicellular and other small algae. 
Many of the genera are easily kept in the laboratory. It is not 
necessary to have very large aquaria. Ordinary glass battery jars 
holding about a gallon are good for most forms. Jars holding 2 gal¬ 
lons will be as good or better. For some cultures which are to 
be kept for a long time, like Scenedesmus, small glass jars, or dishes, 
with ground-glass tops are desirable. For a limited amount of 
material, quart or 2-quart fruit cans are very efficient. Put about 
an inch of pond dirt in some, clean sand in others, and in still others 
use a gravel bottom. Many forms grow well without any soil or 
sand in the bottom of the jar. 
173 
