Species are but convenient groups, their limits reflecting the judgment of the species-maker. Were the authors of this text to divide _Prunus persica_, the cleavage lines would be other than those indicated in the foregoing paragraphs. _Prunus persica_ might be divided, though there is no intention of furthering confusion by the addition of new names, into two species. One would include the white-fleshed, clingstone peaches, with large flowers and calyx greenish-yellow inside; the other the yellow-fleshed, freestone peaches, with small flowers and calyx-cups orange inside. Primitive forms in China indicate such a division, the evolution of varieties suggests it and the present disposition of the characters named as separating these theoretical species attest the reasonableness of such a separation. The primitive forms have been described and the descent of varieties may be traced in the last two chapters, so that we need only amplify the statement as to the present disposition of characters. The characters in the two hypothetical species have been thoroughly shuffled by hybridization but even if there is not correlation, as there certainly is between color in calyx-cup and color of flesh, it might be expected that those associated in the primitive plant, the Adam of the race, would, despite the shuffling, still be most often associated. What are the facts? In the Station orchard are 109 white-fleshed peaches; 40 per ct. of these are semi-cling or clingstones leaving 60 per ct. nearly or quite free (there is constant selection for freestones); 64 per ct. have large flowers; all have calyx-cups yellowish-green inside. There are in this orchard 106 yellow-fleshed peaches; but 17 per ct. of these are cling or semi-cling, the remainder being either quite free or nearly so; 73 per ct. have small or medium-sized flowers; all have calyx-cups deeply colored with orange inside. Similarities in characters indicate so close a relationship between the almond and the peach that one might well suspect many hybrids between the two. Yet there appear to be but few clear cases of peach and almond crosses. Knight[169] reports crossing the two, the doubtful results of which led him to believe, as we have seen, that the peach is but a modified almond. Several such crosses are indicated in botanical literature[170] but whether all refer to one or several supposed crosses there is no way of knowing--probably to one. The almond blooms so much earlier than the peach that crosses could hardly occur in nature. A hybrid between the two from which could be evolved a late-blooming almond is a consummation to be wished. [Illustration: CHINESE FREE (Medium Flowered)] [Illustration: CROSBY (Small Flowered)] THE NECTARINE