I remembered that the Hedeby find shows a piece of whipcord-style braid (I take no position whether it was made by the whipcord method or some other means) sewn onto a part of the dress, but I couldn't remember whether the braid was sewn over a seam or somewhere else.
I was thinking of this, because it occurred to me that if the braid was sewn over a seam that might be further support for the idea that the Hedeby fragment came from a fitted, closed-tube type apron dress that had to be wriggled into. Why? Because braids were sometimes sewn over a seam to strengthen the seam.
However, the braid on the Hedeby fragment was *not* sewn over the seam; it was sewn over the *dart*. Beatson observed:
The top margin, which is made from the selvedge of the fabric, is turned under once and fixed with an elaborate hemming seam. The sides - one is cut straight and perpendicular to the selvedge, the other somewhat curved - must have been seam positions, as they still bear traces of stitch holes. Parallel to the straight edge, and starting about 7cm from the top, a simple dart has been formed using running stitch, and a braided cord has been applied to the ridge thus formed using whip stitch.
Based upon these observations, Beatson suggests that there was a line of braid extending down each side of the dress, starting over the dart positions, and continuing up to the top edge and down to the hem.
I'm not sure what to make of this. Was the braid purely decorative, or did it actually serve a function in this position? The herringbone stitch at the top edge hem likely did serve a function--it secured the top edge, which, if the dress truly was fitted, would receive a lot of stress, while preserving some stretch to aid the fit. Beatson observed: "Ingenious use of a selvedge [for the top edge] made this margin firm, and the sewing technique with which it was hemmed acted like modern zig-zag stitch, able to stretch without breaking."
That observation does tend to support the idea that the dress was a slightly flared, but fitted, tube. But why put the braid over the darts? To discourage twisting of the dress in wear?
Maybe I need to place braid on my dress (when I resume sewing it) and find out. I did place a selvedge along the top edge, but it's a fairly soft selvedge, so I'm not sure it will have the same effect Beatson suggested this use of the selvedge had for the original garment.