The Mendelians, when the mutations of _Oenothera_ were first described, endeavoured to show that they were merely examples of the segregation of factors from a heterozygous combination. They suggested in fact that _Oenothera Lamarckiana_ was the result of a cross, or repeated crosses, between plants differing in many factors, that the numerous mutations were similar to the variety of different types which are produced by breeding together the grey mice arising from a cross between an albino and a Japanese waltzing mouse in Darbishire's experiment. Since that time, however, the natural distribution and the cultural history of _Oenothera_ has been very thoroughly worked out. _Oenothera Lamarckiana_ is the common Evening Primrose of English gardens. The species of the sub-genus _Onagra_ to which _Lamarckiana_ belongs were originally confined to America (Canada, United States, and Mexico), but _Lamarckiana_ itself has never been found there in a wild state. Attempts, however, to produce it by crossing of other forms have not succeeded, and a specimen has been discovered at the Muséum d'Histoire Naturelle at Paris, collected by Michaux in North America about 1796, which agrees exactly with the _Oenothera Lamarckiana_ naturalised or cultivated in Europe. The plant was first described by Lamarck from plants grown in the gardens of the Muséum d'Histoire Naturelle, under the name _OE. grandiflora_, which had been introduced by Solander from Alabama, but Seringe subsequently decided that Lamarck's species was distinct from _grandiflora_, and named it _Lamarckiana_. Gates states that Michaux was in the habit of collecting seeds with his specimens, and that it is therefore highly probable that Lamarck's specimens were grown directly from seeds collected in America by Michaux. Gates considers that the suggestion of the hybrid origin of _Lamarckiana_ in culture is thus finally disposed of. By the year 1805, _Lamarckiana_ was apparently naturalised and flourishing on the coast of Lancashire, and in 1860 it was brought into commerce, probably from these Lancashire plants, by Messrs, Carter. The cultures of De Vries are descended from these commercial seeds, but the Swedish race of _Lamarckiana_, as well as those of English gardens, differ in several features and must have come from another source or been modified by crossing with _grandiflora_. This last remark is quoted from Gates, but it seems improbable that the Dutch plants should be derived from those of Lancashire, and those of English gardens from a different source. The fact seems to be, according to other parts of Gates's volume, that there are various races of _Lamarckiana_ in English gardens and in the Isle of Wight, as well as in Sweden, etc., and that these races differ from one another less than the mutants of De Vries and his followers.