MACROCYSTIS PYRIFERA, OR MAGELLAN KELP.
"A Naturalist's Voyage Round the World" by Charles Darwin
The Macrocystis pyrifera, an Algae, is the largest of all known plants.
"Scientific American Supplement, No. 384, May 12, 1883" by Various
Macrocystis and Nereocystis are also giant members of this sub-order.
"Sea-Weeds, Shells and Fossils" by Peter Gray