This arboretum is not intended to be formally arranged, but to be so planned that it may present all the most beautiful features of lawn and wood-land landscape, and at the same time preserve the natural order of families, so far as may be practicable. The botanical student will thus be able to find any tree or shrub without difficulty. We have selected this tract, of about 40 acres, in the upper angle of the site, so as to interfere with the more special requirements of the park as little as possible. The spot chosen is in some measure separated from the rest of the grounds, by a ridge of land between Fifth and Sixth avenues, and includes the buildings on Mount St. Vincent. The wooden structures would be removed, and the brick chapel converted into a museum and library of botany, similar to that at Kew, but with more specific regard to landscape and decorative gardening. In the park itself there will be numerous specimens of all the trees, native or foreign, that are likely to thrive; but it is proposed to limit this particular collection to American trees, because the space necessary for a complete arboretum would occupy several hundred acres, and also because it will afford an opportunity to show the great advantage that America possesses in this respect. No other extra-tropical country could furnish one quarter the material for such a collection. In the whole of Great Britain, for example, there are less than twenty trees, native to the island, that grow to be over 30 feet in height; while in America we have from five to six times that number. There are, indeed, already over forty species of the largest native trees standing in the park, which is nearly equivalent to the number to be found in all Europe. It is proposed to plant from one to three examples of each species of tree on open lawn, and with sufficient space about each to allow it to attain its fullest size with unrestricted expanse of branches; the effect of each tree is also to be exhibited in masses, so as to illustrate its qualities for grouping. Space is provided to admit of at least three specimens of every native which is known to flourish in the United States north of North Carolina; also for several specimens of every shrub; these latter, however, except in particular instances, are not expected to be planted singly, but in thickets, and as underwood to the coppice masses; as may best accord with their natural habits, and be most agreeable to the eye. Further details of this part of the design will be found in the explanatory guide to the arboretum, submitted with the plan, in which the proposed arrangement of all the trees is set forth in order. * * * * *