  We present the results of SPH simulations in which two clouds, each having
mass $M_{_{\rm{o}}}\!=\!500\,{\rm M}_{_\odot}$ and radius
$R_{_{\rm{o}}}\!=\!2\,{\rm pc}$, collide head-on at relative velocities of
$\Delta v_{_{\rm{o}}} =2.4,\;2.8,\;3.2,\;3.6\;{\rm and}\;4.0\,{\rm km}\,{\rm
s}^{-1}$. There is a clear trend with increasing $\Delta v_{_{\rm{o}}}$. At low
$\Delta v_{_{\rm{o}}}$, star formation starts later, and the shock-compressed
layer breaks up into an array of predominantly radial filaments; stars condense
out of these filaments and fall, together with residual gas, towards the centre
of the layer, to form a single large-$N$ cluster, which then evolves by
competitive accretion, producing one or two very massive protostars and a
diaspora of ejected (mainly low-mass) protostars; the pattern of filaments is
reminiscent of the hub and spokes systems identified recently by observers. At
high $\Delta v_{_{\rm{o}}}$, star formation occurs sooner and the
shock-compressed layer breaks up into a network of filaments; the pattern of
filaments here is more like a spider's web, with several small-$N$ clusters
forming independently of one another, in cores at the intersections of
filaments, and since each core only spawns a small number of protostars, there
are fewer ejections of protostars. As the relative velocity is increased, the
{\it mean} protostellar mass increases, but the {\it maximum} protostellar mass
and the width of the mass function both decrease. We use a Minimal Spanning
Tree to analyse the spatial distributions of protostars formed at different
relative velocities.
