There is a great diversity of opinion among botanists as to what Linnaeus meant to include in his _Prunus insititia_. His description of the species is not definite and can be made to apply to any one of several very distinct plums. But the botanists who recognize the species usually include in it, among cultivated plums, the Bullaces and the Damsons, plums which differ only in the shape of the fruit, the former being round and the latter oval. Some of the texts noted in the references for this species also place the St. Julien and the Mirabelle plums here. In _The Plums of New York_ the authors consider the Bullaces, Damsons, the St. Julien and the Mirabelles as belonging to this species. It is true that Linnaeus established at an earlier date than the naming of _Prunus insititia_ his _Prunus domestica damascena_, in which the varietal name indicates that he meant the Damsons, but the description of the variety taken by him from Bauhin’s Pinax[60] making the plum large, sweet and dark purplish, cannot be made to apply to this fruit, nor can it be connected definitely with any other plum; this being true, and since Linnaeus refers to no type specimen, figure, or locality, his _Prunus domestica damascena_ according to current botanical practices in America, should be rejected. The trees of the Insititia varieties are readily distinguished from the Domestica sorts in having a dwarfer and more compact habit; much smaller and more ovate leaves with more closely serrate margins; branches more finely divided, more slender, with shorter joints, and bearing spines or spinescent spurs; having a more abundant and a more clustered inflorescence, with smaller flowers, a glabrous instead of a pubescent pistil and calyx-tube; reflexed calyx-lobes where in Domestica they are often erect; and flowers appearing nearly a week later. The number of stamens in _Prunus domestica_ averages about thirty; in _Prunus insititia_, about twenty-five. The fruit-characters of _Prunus insititia_ are even more distinctive. The fruits are smaller, being less than an inch in diameter, more nearly round or oval, more uniform in shape, never strongly compressed as in Domestica, with a less distinct suture and more often with a pronounced neck. The color is usually the Damson purple or the Mirabelle yellow, with no intermediate colors as in Domestica and with few or but slight variations as compared with the other species. The plums are sweet or sour with a very much smaller range in flavor in the case of the Insititias and withal very distinct from that of _Prunus domestica_. The stones are smaller, more oval and much more swollen.