4. These differences of proportion of ligule and stalk are obviously correlated with the different habits of the two species. The shorter and more robust trunk of the one enables it to withstand the strain of the relatively limited exposure to the wind. There is also a greater flexibility in the leaf itself, due to its thinner texture and to the smaller development of the ligule and adjacent thickened area, so that the leaves are often split to near the center. The narrow petiole of the tall species affords greater flexibility in the lateral plane while strength has been secured by the greater thickness. On the other hand the thinness of the base of the petiole of _Thrincoma_ reduces resistance by permitting the petiole to be twisted when the leaf is opposed to the wind or blown laterally, thus avoiding the strain which would come upon the more rigid base of the petiole in _Thrinax_. The more salient differences between the leaf-blades of the two species may be enumerated as follows: 1. Although the length of the middle segments of the leaves of _Thrincoma_ are longer (62 cm.) than those of the other (55 cm.) the apparent size of the latter is much greater because they are fully expanded while those of _Thrincoma_ remain more or less fan-shaped, generally opening less than a semicircle. This decreases the lateral expansion, since the shortest divisions are brought to the sides, and gives no projection below the ligule where in _Thrinax_ more than one third of the foliar expanse is located. 2. The leaf segments are much narrower (3.6 cm.) in the tall than in the short species (4.8 cm.). 3. Practically the difference in width is still greater because the segments of _Thrincoma_ are never fully expanded but remain deeply channelled, thus decreasing the area of exposure to the wind and increasing the rigidity of the leaf. 4. Resistance to the wind is also reduced in the tall species by the separation of all the segments to more than two-thirds their length, while in _Thrinax praeceps_ the median segments are united more than half way up. In the latter, as in the other members of the group, the separation begins at the point of greatest width of the segment, but as if to show that the deeply divided leaves of _Thrincoma_ are an adaptation, the greatest width is located near the longitudinal middle of the segments, 10 cm. or more above the bottom of the cleft. 5. The texture of the leaf of _Thrincoma_ is thicker and firmer so that the segments generally remain straight to the tips while in _Thrinax_ they often droop after the leaves have become fully expanded. 6. The color of the leaves of the tall palm is a very dark green while those of _Thrinax praeceps_ are uniformly of a much lighter, fresher tint. 7. The veinules of the firm leaves of _Thrincoma_ are more numerous and closer together than those of _Thrinax_.