§ 1. Before following farther our inquiry into tree structure, it will rest us, and perhaps forward our work a little, to make some use of what we know already.

It results generally from what we have seen, that any group of four or five leaves, presenting itself in its natural position to the eye, consists of a series of forms connected by exquisite and complex symmetries, and that these forms will be not only varied in themselves, but every one of them seen under a different condition of foreshortening.

The facility of drawing the group may be judged of by a comparison. Suppose five or six boats, very beautifully built, and sharp in the prow, to start all from one point, and the first bearing up into the wind, the other three or four to fall off from it in succession an equal number of points, taking each, in consequence, a different slope of deck from the stem of the sail. Suppose, also, that the bows of these boats were transparent, so that you could see the under sides of their decks, as well as the upper;—and that it were required of you to draw all their five decks, the under or upper side, as their curve showed it, in true foreshortened perspective, indicating the exact distance each boat had reached at a given moment from the central point they started from.