Nymphoides Aquatica

About  5 weeks ago, I purchased two pathetically looking banana plants from
a local store for .98 each.  The little things had a rootstock with two tiny 
leaves each.  I planted the rootstock in the gravel about 1/4 or so of the way
and watched closely over time.  After about two weeks, it had put out two new 
leaves about 1"-1.5" in diameter and relatively close to the rootstock.  

After about 5 of these leaves, some about 3"-3.5" in diameter, both plants have
put out shoots that have floating leaves.  

Which brings me to my question.  In James' book, it states that they are 
propagated by dividing the rootstock, runners, or plantlets.

Since I have not seen any plantlets, I was wondering if anyone has separated the
rootstock on this species.

If not, how can I safely propagate them?  I read in the archives that the floating 
was cut by one guy and it regrew a new plant.

I have taken a real liking to these plants, especially after I bought them as an 

Any experience with these?

Tyson Lee
tyson at phoenix_net