226 PLANT STUDIES 
of the compound microscope to marine forms with enor- 
mously bulky bodies. In general they are hydrophytes 
that is, plants adapted to life in water or in very moist 
places. The special interest connected with the group is 
that it is supposed to be the ancestral group of the plant 
kingdom the one from which the higher groups have been 
more or less directly derived. In this regard they differ 
from the Fungi, which are not supposed to be responsible 
for any higher groups. 
155. The subdivisions. Although all the Algae contain 
chlorophyll, some of them do not appear green. In some 
of them another coloring matter is associated with the chlo- 
rophyll and may mask it entirely. Advantage is taken of 
these color associations to separate Algae into subdivisions. 
As these colors are accompanied by constant differences in 
structure and work, the distinction on the basis of colors is 
more real than it might appear. Upon this basis four sub- 
divisions may be made. The constant termination phycece, 
which appears in the names, is a Greek word meaning " sea- 
weed," which is the common name for Algae; while the pre- 
fix in each case is the Greek name for the color which char- 
acterizes the group. 
The four subdivisions are as follows : (1) Cyanophycece, 
or " Blue Algae," but usually called " Blue-green Algae," as the 
characteristic blue does not entirely mask the green, and 
the general tint is bluish-green ; (2) Chlorophycem, or " Green 
Algae," in which there is no special coloring matter associ- 
ated with the chlorophyll ; (3) Phceophycece, or " Brown 
Algae " ; and (4) Rhodophycece, or " Eed Algae." 
It should be remarked that probably the Cyanophyceae 
do not belong with the other groups, but it is convenient to 
present them in this connection. 
156. The plant body. By this phrase is meant the nutri- 
tive or vegetative body. There is in plants a unit of struc- 
ture known as the cell. The bodies of the simplest plants 
consist of but one cell, while the bodies of the most com- 
