  The plasma {\beta} (the ratio of the plasma pressure to the magnetic
pressure) of a system can have a large effect on its dynamics as high {\beta}
enhances the effects of pressure anisotropies. We investigate the effects of
{\beta} in a system of stacked current sheets that break up into magnetic
islands due to magnetic reconnection. We find significant differences between
{\beta} < 1 and {\beta} > 1. At low {\beta} growing magnetic islands are
modestly elongated and become round as contraction releases magnetic stress and
reduces magnetic energy. At high {\beta} the increase of the parallel pressure
in contracting islands causes saturation of modestly elongated islands as
island cores approach the marginal firehose condition. Only highly elongated
islands reach finite size. The kinking associated with the Weibel and firehose
instabilities prevents full contraction of these islands, leading to a final
state of highly elongated islands in which further reconnection is suppressed.
The results are directly relevant to reconnection in the sectored region of the
heliosheath and possibly to saturation mechanisms of the magnetorotational
instability in accretion flows.
