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 ])hyce(B^ 

 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) CyanophycecB^ 

 or " Blue Algae," but usually called " Blue-green Algse," as the 

 characteristic blue does not entirely mask the green, and 

 the general tint is bluish-green ; (2) Chlorophycece^ or " Green 

 Algae," in which there is no special coloring matter associ- 

 ated with the chlorophyll ; (3) PhcsophycecB, or " Brown 

 Algae " ; and (4) Rhodophycece^ or " Red 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- 



