starchwort

from The Century Dictionary.

• noun The wake-robin, Arum maculatum, whose root yields a starch once used for fine laundry purposes, later prepared as a delicate food under the name of English or Portland arrowroot. This was chiefly produced in the Isle of Portland, where the plant is called starchroot. See cuts under Araceæ and Arum.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) The cuckoopint, the tubers of which yield a fine quality of starch.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The plant cuckoopint, the tubers of which were once used to make starch