SPIRE 250 μm map with extinction contours (Schneider et al. 2011) overlaid from 2 to 10 mag, in steps of 2 mag. The arrows show the general orientation of the magnetic field as measured in Cha I by Whittet et al. (1994) and McGregor et al. (1994). Note the preferential alignment of the faint striations in Cha I, which are less evident in Cha II or Cha III, where the surrounding diffuse emission takes a variety of orientations. In the region eastwards of Cha III, no striations are detected in the Herschel maps.