226 PLANT STUDIES 



of the fomponnd microscope to marine forms witli eiior- 

 moiisly bulky bodies. In general they are li ydrdpliiites — 

 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 ]ilant 

 kingdom — the one from which tlie higher groups liave been 

 more or less directly derived. In this regard they differ 

 from the Fungi, whicli are not supjiosed to l)e responsilde 

 for any higher groups. 



155. The subdivisions. — Although all the Algfe contain 

 chlorophyll, some of them do not ajjpear green. In some 

 of them another coloring matter is associated witli the chlo- 

 rophyll and may mask it entirely. Advantage is taken of 

 these color associations to separate Algaj 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 ap)pear. Upon this basis four sub- 

 divisions may be made. The constant termination phijrea', 

 which appears in the names, is a Greek word meaning " sea- 

 weed," wliicli is the common name for Algii? ; while the pre- 

 fix in each case is the Greek name for the color wliicli char- 

 acterizes the group. 



Tlie four subdivisions are as follows: (1) C'iiauop]tii<-i'(p, 

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

 cliaracteristic blue does not entirely mask tlie green, and 

 tlie general tint is l)luisli-green ■ (2) ( ']il(in)phijvru\ or " Green 

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

 ated with the chlorophyll ; (3) PJiwnplnjrKP^ or " Brown 

 Alg;e " ; and (4-) Tlhodopliyci'CP, or " Red Alg:e." 



It should l)e remarked that proliably tlie ('yanophycea» 

 do not belong with the other groups, but it is convenient to 

 present them in this connection. 



150. The plant body. — By this plirasc is uu'ant the nutri- 

 tive or vegetative liody. There is in plants a unit of struc- 

 ture known as the cell. Tlie bodies of the simjilcst plants 

 consist of but one cell, while the bodies of tlie most com- 



