THALLOPHYTA , 339 
the Chlorophyceae, the Phaeophyceae show a great variety of 
forms (Figs. 851-353) and various degrees of sexual differen- 
tiation. The Phaeophyceae are found mostly in salt water. They 

Fig. 351. Brown alge 
Above, Sargassum (x 3); note that the plant is divided into stemlike and leaf- 
pee portions and also has rounded air bladders which contain air and add to the 
buoyancy of the plant. Below, Padina australis (x 3) 
include the largest and some of the most conspicuous seaweeds. 
A simple form is Hetocarpus, in which the vegetative body con- 
sists of branched filaments composed of single rows of cells 
