John Ray published the first Flora of Cambridgeshire just over three hundred years ago, and since then the study of our local plants has been almost continuous. Relhan (1785) and Babington (1860) published further Floras at approximately hundred-year intervals, and this Flora was first planned by the Cambridge Natural History Society to appear in 1960, the tercentenary of Ray's work. Unfortunately we underestimated the amount of work involved, and regretfully decided to abandon the original date.

This work, based upon the Natural History Society's records, departs from the standard practice of most local Floras in that it does not give long lists of localities under each species. In their place is a concise list of Ordnance Survey Grid References which give an adequate picture of the main features of distribution of the species. The space saved allowed us to include taxonomic notes, comments and keys, which we believe will prove to be more valuable than the traditional distribution data.

1519 species are listed, of which 27 are Pteridophyta, 3 Gymnospermae, 1228 Angiospermae and 261 Bryophyta. Of the 1231 seed plants, 968 are native (65 of these being extinct), 19 are doubtfully native, 81 are naturalized, 31 are planted trees, and 195 casuals, garden escapes or relics of cultivation. Of the 27 Pteridophyta one is introduced and nine extinct. Of the Bryophyta 222 are mosses (20 extinct) and 39 liverworts (4 extinct).