Not Art Nouveau. Late 1800s early 1900s seems reasonable, but the style is not Nouveau.
I see in your other post you mention rosewood. The only rose flower bush wood I've seen used was from the root, so I can't say anything about the cane shaft, other than the twig knots seem far too regular for a rose bush.
There are about 40 different trees called rose wood, and I've seen the wood from a few. Alas, no help in identifying your cane shaft.
Where did you find the stick? Sometimes having a date and location for the original owner helps narrow things down.
A forum community dedicated to walking stick owners and enthusiasts. Come join the discussion about modifications, collections, woodworking, canes, styles, scales, reviews, accessories, classifieds, and more!