ALGM CONTIA'UED: CLASSIFICATION. 



167 



^th new valves. The valves are often marked with nunierous and fine 

 lines, often making beautiful figures, and some are used for test oVjjects for 

 microscopes. 



The free forms are capable of movement. The movement takes place in 

 the longitudinal direction of the vah'es. They glide for some time in one 

 direction, and then stop and move back again. It is not a dilTicult thing to 

 mount them in fresh water and observe this mo\'cment. 



The diatoms have small chlorojihyll plates, but the green color is dis- 

 guised by a brownish pjigmcnt called diatomin. Tlic relationships of the 

 diatoms are uncertain, but some, because of the color, think they are re- 

 lated to the Ph;eophyce;e. 



Class Phaeophyceae. 



369. The brown algae. (Phaeophyceae). — The members of this class pos- 

 sess chlorophyll, Vjut it is oVjscured by a brown pig- 

 ment. The ]>lants are accessible at the seashore, 

 and for inland laboratories may be preserved in 

 formahn (2! per cent). (See also Chapter LVI.) 



360. Ectocarpus. — The genus Ectocarpus repre- 

 sents well some of the simpler forms of the brown 

 algie (fig. 172). They are slender, filamentous 

 branched alga; growing in tufts, either epiphytic on 

 other marine algse (often on Fu'-aceae), or on stones. 

 The slender thrvarls are o:dy divided crossmse, 

 and thus consist of long series of short cells. The 

 sporangia are usually plurilocular (sometimes uni- 



B 



E 



Fig. 172. 

 4 Ectocarpus siliculosus; B. branch with a young and a ripe 

 plurilocular Tporangmm; £, gametes fusmg to form zygospore. 

 (B, after Thuret; £, after Berthold.J 



