"brown moss" should include all the forms which 

 are not definitely green.) 



The characteristic fouling forms consist of 

 mats of long slender threads or filaments, usual- 

 ly branched (fig. 7, A, B, and E) . Others have 

 fronds resembling ribbons or leaves of lettuce 

 (fig. 7, D), and still others (known as rock- 

 weeds) have hollow swellings which serve as 

 floats (fig. 7, C). 



It is desirable to distinguish between green 

 and brown algae. The latter are considered more 

 objectionable in that they adhere more tightly. 

 Consequently they often tear off the paint in the 

 wind and water area which is then subject to in- 

 creased fouling and corrosion. 



HYDROIDS 



Hydroids (figs. 8 and 9) are small animals 

 with slender stalks. Joined together like Sia- 

 mese twins, they usually live in plantlike col- 

 onies composed of many individuals. Each branch 

 of a colony represents a single individual. At 

 the end of each branch is a flowerlike expansion, 

 frequently pink in color. These expansions read- 

 ily distinguish Hydroids from the branching types 

 of Bryozoa. When attached to a hull, Hydroids 

 often form a pale cream or tan mat which may be 

 very thick and extensive. 



For a discussion of the term Eydroides , see 

 page 11. 



18 



