The well-developed light line in _Melilotus alba_ and _M. officinalis_ is found just below the bases of the cones. In some seed coats only a few and in others none of the canals which are common in the cones and cuticularized region cross the light line. A very distinct line of small canals filled with air and thus forming a dark band is present just above the fight line, thus making the light line more conspicuous. (Pl. V, fig. 3.) When the lumina of the cells extend across the light line, they are exceedingly small. The light line is the most compact region of the Malpighian layer and is conspicuous because it refracts the light much more than the regions above and below it. Just below the Malpighian is a layer of cells variously modified and known as the osteosclerid. The cells of this layer are often referred to as the hourglass cells on account of their shape. In some regions of the seed coat they are expanded at both ends and their walls are much thickened, the thickenings forming ridges on the radial walls, while in other regions only the upper tangential wall and a portion of the radial walls are thickened and the cells are expanded only at the inner end, thus having the shape of the frustum of a cone. Beneath the osteosclerid layer is the nutrient layer. The nutrient layer contains chloroplasts. It varies not only in the number of layers of cells composing it, but also in the modifications of these cells. This layer ranges from four to seven cells in thickness in the different parts of the seed coat. PLATE V. [Illustration] Structure of the Seed Coat of Sweet Clover.