The various species of Primula have produced in a state of nature throughout Europe an extraordinary number of hybrid forms. For instance, Professor Kerner has found no less than twenty-five such forms in the Alps. The frequent occurrence of hybrids in this genus no doubt has been favoured by most of the species being heterostyled, and consequently requiring cross-fertilisation by insects; yet in some other genera, species which are not heterostyled and which in some respects appear not well adapted for hybrid-fertilisation, have likewise been largely hybridised. In certain districts of England, the common oxlip–a hybrid between the cowslip (P. veris, vel officinalis) and the primrose (P. vulgaris, vel acaulis)–is frequently found, and it occurs occasionally almost every-where. Owing to the frequency of this intermediate hybrid form, and to the existence of the Bardfield oxlip (P. elatior), which resembles to a certain extent the common oxlip, the claim of the three forms to rank as distinct species has been discussed oftener and at greater length than that of almost any other plant. Linnaeus considered P. veris, vulgaris and elatior to be varieties of the same species, as do some distinguished botanists at the present day; whilst others who haye carefully studied these plants do not doubt that they are distinct species. The following observations prove, I think, that the latter view is correct; and they further show that the common oxlip is a hybrid between P. veris and vulgaris.