The Zygnematales also called the Conjugales , are an order of green algae , comprising several thousand different species in genera such as the well-known Zygnema and Spirogyra . , Î 1\/2 Î Î 1\/4 Î Ï Î Ï ( nÄ `` matos ) ( gen. ) ) , also called the Conjugales , are an order of green algae , comprising several thousand different species in genera such as the well-known Zygnema and Spirogyra .