  We search for a direct signature of discrete ''clouds'' in the broad line
region (BLR) of the Seyfert galaxy NGC 4151. For this purpose we apply cross
correlation (CC) analysis to a high resolution KECK spectrum of the galaxy. No
such signature is found in the data. In order for cloud models to be compatible
with this result, there must be at least $\sim3\times10^7$ emitting clouds in
the BLR, where the limit is based on simulation of a homogeneous cloud
population. More realistic distributions increase the lower limit to above
$10^8$. These numbers are an order of magnitude improvement on our previous
limit from Mrk 335, where the improvement comes from higher S/N, broader lines,
and refined simulations. Combined with the predicted upper limit for the number
of emitting clouds in NGC 4151 ($10^6-10^7$), the derived lower limit puts a
strong constraint on the cloud scenario in the BLR of this object. Similar
constraints can be paled on models where the emission originates in streams and
sheets. Thus, this investigation suggests that the BELs in NGC 4151, and by
extension in all AGNs, are not made of an ensemble of discrete independent
emitters.
