I am trying to figure out what style/genre of art is displayed in the leftmost card in this picture. I am specifically referring to the brown design element that for lack of a better word I will describe as a "tree." I don't think it is art nouveau, but I could be wrong. What do the art historians think?
I am not an art historian, so I will not able to provide you with more interesting information, but the look of this set of cards is unmistakably art nouveau. In fact, use of floral and vegetal forms and patterns was probably the most distinctive and ubiquitous marks of this artistic movement—they were a powerful symbol of the organic unity of art and life, and even when they are not apparent, the curves and bends of virtually every art nouveau work are reminiscent of this natural inspiration.
It is very certainly is Art Noveau; in fact to my mind it least it seems to be very much a cross between the interior design of Victor Horta(http://4.bp.blogspot.com/_RoYDEP8CaHI/STSXVznqv8I/AAAAAAAAADA/jLtKClmWzeU/s400/slide_11.jpg) and Charles Rennie Mackintosh http://www.wmf.org/sites/default/files/imagecache/project/images/project/E.1981.177.jpg.
