The seed of Pinus contains an embryo, with the cotyledons clearly defined, embedded in albumen, which is protected by a bony testa with an external membranous spermoderm, produced, in most species, into an effective wing. While the seed of other genera of the Abietineae shows no striking difference among the species, that of Pinus is remarkably variable, presenting alike the most primitive and the most elaborate forms among the Conifers. These differences are valuable for the segregation of kindred species and for some specific distinctions. WINGLESS SEEDS. With wingless seeds the main distinction is found in the spermoderm, which is entire in one species only, P. koraiensis. In P. cembra it is wanting on the ventral surface of the nut, but on the dorsal surface, it is adnate partly to the nut, partly to the cone-scale. The nut of P. albicaulis and that of P. cembroides are quite bare of membranous cover. The spermoderm of P. flexilis is reduced to a marginal border, slightly produced into a rudimentary wing adnate to the nut. THE ADNATE WING. In P. strobus, longifolia and their allies and in P. Balfouriana the spermoderm is prolonged into an effective wing-blade from a marginal adnate base like that of P. flexilis. This adnate wing cannot be detached without injury. THE ARTICULATE WING. The articulate wing can be removed from the nut and can be replaced without injury. An ineffective form of this wing is seen in the Gerardianae and in P. pinea, where the blade is very short and the base has no effective grasp on the nut. The base of the effective articulate wing contains hygroscopic tissue which acts with the hygroscopic tissue of the cone-scales. The dry conditions that open the cone and release the seeds cause the bifurcate base of the wing to grasp the nut more firmly. This articulate wing is found in P. aristata and in all Hard Pines except P. pinea, longifolia and canariensis. The wing-blade is usually membranous throughout, but in some species there is a thickening of the base of the blade that meets the membranous apical part in an oblique line along which the wing is easily broken apart. This last condition attains in P. Coulteri and its associates a remarkable development. Plate VI, fig. 72 shows the wingless seed of P. cembroides; fig. 73 represents the seed of P. flexilis, with a rudimentary wing; fig. 74 shows two seeds of P. strobus, intact and with the wing broken away; fig. 75 represents the articulate wing, whose bifurcate base when wet (fig. 76) tends to open and release the nut. When dry (fig. 77) the forks of the base, in the absence of the nut, close together and cross their tips; figs. 78, 79 show the peculiar reinforced articulate wing of P. Coulteri.