providing {TAIL ~ a growing surface} in said water to which said algal spores form {HEAD ~ an attachment} 
providing { TAIL ~ a growing surface } in said water to which said algal spores form { HEAD ~ an attachment }
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD