Sentence:  A <WSD>double exposure</WSD> from the 1960's seems to make explicit some of the implications of Cunningham's own early plant studies. In it, ghostly hands appear on top of the image of an aloe plant, with fingers and fronds jumbled together, all outstretched and reaching. 
Meaning of the word marked with <WSD> tags:  A photograph produced by exposing film or some other photosensitive surface to focused light twice, usually by opening and closing a camera shutter two times, thereby generating a picture consisting of two superimposed images.