This paper consists in an investigation of the collineations of a class of planes
constructed by the author. The construction consists of replacing the lines of a net
embedded in a given plane by subplanes of the same net.
For the case in question, the given plane is the dual of a translation plane. The
full collineation group of the new plane is isomorphic to a subgroup of the
collineation group of the original plane. The main point of the argument is
to show that the new planes admit no collineations displacing the line at
infinity.
