3. In order to support the weight and strain of this greater height, the texture of the wood is extremely hard and firm, especially near the base of the trunk. Externally it is covered by a smooth shell or bark of very hard, brittle, dark colored material. The fibers of the interior which in _Thrinax_ are merely imbedded in a soft pith like those of a corn-stalk are here thickened and cemented together, as in tall palms of other groups, into a dense hard wood. In the specimen cut by us all but a small area of the middle of the trunk was thus hardened, rendering it extremely heavy. The wood-fibers of _Thrincoma_ are much coarser than those of _Thrinax_, and there appear to be none of the obliquely radial threads which are abundant in the wood of _Thrinax Ponceana_. With reference to methods of leaf-attachment four differences may be noted: 1. In _Thrinax praeceps_ the leaf-bases split below in the median line and remain long attached to the trunk. This adaptation is not confined to the old leaves but appears while the leaves are still very young, or as soon as they begin to be expanded by the pressure of those above them. In the tall species such pressure separates the fibers of the opposite side of the cylinder. The short species has the outside of the leaf-bases densely tomentose, and the tomentum is especially abundant along the edges of the split midrib of the young leaf. 2. The ligule of _Thrincoma_ is notably larger than that of _Thrinax_ and continues to lie in the same plane as the blade, and becomes brown with maturity. In old leaves of _Thrinax_ the ligule stands nearly at a right angle to the blade and remains green. 3. For leaves of the same size the petioles, not including the sheathing base, are longer (75–80 cm.) in the short than in the tall species (60–65 cm.). The petiole of the short species is of nearly the same width (1.2–1.5 cm.) throughout, while in the other it is distinctly broader at both ends than in the middle. The enlargement at the ligule is abrupt. The base widens gradually to about 2 cm. but is much thinner than in the short species. In the upper part of the petiole the reverse is true, the cross section of the leaf-stalk of the _Thrincoma_ being almost diamond-shape, while that of _Thrinax_ is merely lenticular.