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Mr. Darwin has sent us two pamphlets, reprints from the Linnean Society's Journal, which  show that he is continually adding to the vast store of botanical facts recorded in his work on Animals and Plants under Domestication. These memoirs are of too great length, and  embrace too many important details, to admit of our giving a satisfactory abstract of them  here. We therefore briefly record some of the conclusions of their author, and refer our  readers to the Linnean Society's Journal (Botany, vol. x.) for further information. In one of  the papers –"On the specific Difference between Primula veris, P. vulgaris, and P. elatior, and on the hybrid Nature of the common Oxlip" –Mr. Darwin proves, as we think  satisfactorily, that the three first forms are specifically distinct, and that the oxlip is merely a  hybrid. The results of the different "crossing" experiments are so lucidly tabulated, that the  evidence in favour of the author's opinion may be seen at a glance. Mr. Darwin regards the  oxlip as a hybrid between the cowslip (P. veris, Brit. Fl.) and the primrose (P. vulgaris, Brit.  Fl.), as has been surmised by various botanists. He thinks it probable that the oxlips may be  produced either from the cowslip or the primrose as seed-bearer, but oftenest from the  latter, as he judges from the nature of the stations in which oxlips are generally found, and  from the primrose, when crossed by the cowslip, being more fertile than the cowslip by the  primrose. Mr. Darwin also demonstrates the specificity of Primula elatior. The title of Mr.  Darwin's second memoir is sufficient to indicate the mass of valuable facts the paper  contains, and the painstaking and laborious inquiries which have been undertaken by the  author. It is "On the Character and hybrid-like Nature of the Offspring from the illegitimate  Unions of dimorphic and trimorphic Plants." The plants dealt with here are Lythrum Salicaria,  Oxalis rosea, Primula sinensis, P. auricila, P. vulgaris, P. veris, and Pulmonaria. The general  conclusion which the author draws is one of the highest interest, for it in part solves one of the most serious objections (that of the sterility of species) raised against the theory of the  origin of species by natural selection. This conclusion is. partially expressed in saying that the illegitimate offspring from an illegitimate union are hybrids formed within the  limits of one and the same species. In proof of the importance of recognising the infertility  existing between certain sexual forms of dimorphic and trimorphic plants, Mr. Darwin says:  "If any one were to cross two varieties of the same form of Lythrum or Primula, for the sake  of ascertaining whether they were specifically distinct, and he found that they and their  offspring were extremely sterile, and that they resembled in a whole series of relations  crossed species and their hybrid offspring, he would maintain that his varieties had been  proved to be good and true species; but he would be completely deceived."