Isolated chloroplast membranes of the unicellular photosynthetic alga Chlamydomonas reinhardtii were exposed to low salt buffer, cryofixed, freeze-fractured, and surface replicas observed by transmission electron microscopy. Under these conditions, thylakoid membranes from wildtype cells show the particle size and distribution typical of unstacked membranes. See Fig 22 in Goodenough and Staehelin 1971 J Cell Biol 48:595-619.