Species plantarum. Exhibentes plantas rite cognitas ad genera relatas. Cum diferentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas. 2 vols.

In this work Linnaeus introduced his full binomial naming system for plants (binomial nomenclature).  Describing about 8,000 plant species from all over the world, the book demonstrated the value of a binomial system of nomenclature for biology generally, and was the stimulus to the development of this type of classification throughout the field.  Digital facsimile from Biodiversity Heritage Library at this link.