[BioC] Help on: Resizing the plot of a dendrogram when plotting clusters

[maon yskmohc]

Hi,

1)
I am trying to resize the plot of a dendrogram when plotting clusters.
clust = hclust(as.dist(dissim), method=clust_method)
plot(clust)

The resulting dendrogram has multiple branches but it is very flat
which makes it difficult to tell apart the branches.
When applying the parameters ylim,xlim to the plot() function they
don't seem to work.
Does anybody know how to resize the plot of the cluster's dendrogram?
In a few words how to make ylim work?

2)
If I run k-means clustering with smaller sets, and plot the result of
the function silhouette() of the cluster package correctly labels each
element in the set,
but when I run it with ~16 elements the labels for the elements
dissappear from the plot.
Does anybody know how to retain the labels for this specific case?

I am attaching a picture of the graphic in each case.

Thanks,
Maon