Alex Purdie was born in Dunedin, New Zealand, where his Scottish father worked for the Otago Museum. He studied at the University of Otago (BA 1882, MA 1884), completing a thesis on mussel anatomy. He also published papers on Lepidoptera during his time as a student. Moving to Wellington, Purdie joined the Philosophical Society but returned to Dunedin to study geology in 1891 at the Otago School of Mines. He then worked as a lecturer at the School before moving to Australia in 1892. There, he was Director of the School of Mines in Sale, Bendigo and Adelaide, successively, before being appointed Director of Technical Education in West Australia. He died at a relatively young age in 1905, of typhoid.

Following in his father's footsteps, Purdie was a keen amateur botanist with a special interest in native Australian orchids. He collected plants mainly in Western Australia and published a number of works. He also lectured in botany at Perth Technical School. Purdie's Donkey Orchid, Diuris purdiei Diels is named in his honour.

Sources:
E.J. Godley, 2004, "Biographical Notes (56): Alexander Callender Purdie (1824-1899) and Alex. Purdie (c.1861-1905)", New Zealand Botanical Society Newsletter, 78(December): 18-19.