I'm a little confused about this…
Firstly… There is a wiki page about a class GeometryBatch by Mike Stoddard (stodge on these forums), which batches meshes into a single object. The advent of this class (or at least it's first mention on these forums) was around November 2005, and continued on to November 2007 at least. It's my impression (but I may be mistaken) that this is for jME2.
BUT ALSO… included as part of the jME2 core libraries there is a set of classes which does the same thing: GeometryBatchCreator which creates GeometryBatchInstances by Patrik Lindegr
OK found some info…
http://www.jmonkeyengine.com/forum/index.php?topic=3884.msg30850;topicseen#msg30850
Apparently GeometryBatch was an unofficial thing (as stated) that stodge wrote way back and is very lightweight but no longer be able to work so easily with modern version of jME(?).
On the other hand, it looks like GeomBatch (which seems to have been deprecated and is replaced by the GeometryBatchInstance classes in the core???) can merge goodies with different render states – I assume the same is true of the new replacement classes then.