vestigial |veˈstij(ē)əl|
adjective
forming a very small remnant of something that was once much larger or more noticeable : he felt a vestigial flicker of anger from last night.
• Biology (of an organ or part of the body) degenerate, rudimentary, or atrophied, having become functionless in the course of evolution : the vestigial wings of kiwis are entirely hidden.

Stems - the side, profile shape of the bow and stern of a boat.

Traditionally canoes and other small boats built with wood have wood stem pieces to which hull boards are fastened. These wood stem pieces are not only used to anchor hull boards but actually create the shape of the stem.

In strip building plywood stem forms define the stem shape and wood hull strips jointed past the stem form rely on fiberglass for strength. Separate stem pieces have become functionless in strip boat construction, being a vestige of traditional wood construction without fiberglass.

You can build a strip canoe without separate stem pieces (vestigial), but you cannot build a traditional wood boat without them.

rob