|i|i i|i|i|imi|iii i|i|i|rii!i|iii|i|i|iii|i|i|i|i i|i|i|ili| 



Figure 28. Plastic vinyl tubes damaged by borers. 



STU 1-2 



Figure 29. Hydroid growth over a roughened section of a nylon rod. 



36 



