Perth Plants Barrett & Tay, Pg 94
UPDATE 31-JUL-2010: New photos of A. pulchella in bloom.
While not currently blooming, the Prickly Moses is making itself known in the park especially along the Law Walk but also in the bushland areas.
A. pulchella blooms in spring (May-Dec) with characteristic yellow, "puff ball" flowers. Even without blossoms, it is an easily recognizable plant with its small leaves, green buds and most importantly if you intend to handle it, the small spikes that give it its name. The name may be a variation of "Prickly Mimosa" but no matter the source, the prickles will let you know for sure what plant you have found when you grab a handful.
The fact that it is most abundant along the Law Walk reinforces verbal information I received stating that it is one of the early re-colonizers after a fire. I invite corrections or substantiation of this "fact" via the comment function below or e-mail.
It is one of very few Acacias that have true leaves rather than phyllodes or modified leaf stems.
I will add some pictures of the A. puchella after they start blooming this spring. Until then you can see the flowers at Florabase by clicking on the reference above.