Lars Spuybroek, the twentieth- and twenty-first-century architect and architectural theorist who is very much a neo-Ruskinian, begins one of his discussions of Art Nouveau by referring to the "pure proliferation" of hair in Mucha's posters, after which he points out that
The curves in Art Nouveau are very different from Hogarth's S-curves. His serpentines have two loose ends; variation progresses all the way through the line, a bit like Pollock's arabesques, but the Art Nouveau curves have both o loose end and a fixed end. They are vegetal: that means they are rooted at one end and loose at the other and move with the wind or the water. As you follow the line, there is an increase of curvature. It starts out quite straight at one end and slowly becomes more curved, and then at the other end there are suddenly three or four extra twists and turns. That's why they often called it a "whiplash," and it's also the reason why Walter Benjamin called Art Nouveau dangerous: because it is an aesthetic of the dreamy and the figures float in the wind or under water, like water plants, which have a similar type of curvature. He thought this dreaminess, which is directly related to the sleeping women in Victorian classicist paintings, like those of Albert Moore, was keeping the revolutionary masses off the streets. 
Spuybroek agrees with Benjamin, who espouses "modernist transparency," that the "Art Nouveau house is a cocoon, a crimson velvet case." — in other words, a Palace of Art, and in this palace one encounters "at once a strange passivity and movement in Art Nouveau. The bodies, mostly female, are almost always asleep, or gazing, daydreaming; the fabric is full of folds, and the hair curls in millions of tendrils. Like the the water plant: fixed on one end, free and moving on the other. Turning to Mucha's "amazing" plates, he sees his works embodying or exemplifying what we may see as the Ruskinian notion of nature's infinite variety:
First, the art of variation is an art of the many. To deploy variation, you need many parts. Then they have to be coordinated: there needs to be a certain similarity of figure or else there is no proliferation. Proliferation is an extremely serial type of variety. Then we need effects that occur in one area to be feeding back into other areas. So it is an art of multiplication, too. One can only do this with curves, continuity. Then, fourth, you have to vary the variations: there are entanglements, strands of multiple hairs, mergences, crossings. See? It's not just hair blowing about in an invisible wind. There are individual hairs that become collective strands or tendrils, and they also form networks of crossings, so there are configuring properties in it. That's essential in this aesthetics, which is a vitalist aesthetics: life and geometry or life and construction are constantly intertwining. 
The "vitalist aesthetics" he mentions, which braid together life and constructed form finds exemplification, one may add, in Ruskin's conception of Vital Beauty.
Spuybroek, Lars. "The Aesthetics of Variation." The Architecture of Continuity: Essays and Conversations. Rotterdam: V_2 Publishing, 2008.
Last modified 20 July 2009