R help - Mar 2005 - Changing label size in plot.dendrogram

Dear R friends,

I have constructed an object of class 'dendrogram'
using an own function, and I'm using the R function
plot.dendrogram for visualizing it.
It works fine, but I could not find out how to change
the font size of edge and leaf labels.
?plot.dendrogram has shown me that the coloring of the
edge labels can be changed using plot(my.dendrogram,
edgePar=list(t.col='green')), but something like
't.cex' doesn't seem to exist.  

Any hints greatly appreciated.
Best regards,
Michael