Choose any tree that you think pretty.
Which is nearly bare of leaves.
Which you can see against the sky, or against a pale wall, or other light ground.
(It must not be against strong light, or you will find the looking at it hurt your eyes; nor must it be in sunshine, or you will be puzzled by the lights on the boughs. But the tree must be in shade; and the sky blue, or gray, or dull white. A wholly gray or rainy day is the best for this practice.)
You will see that all the boughs of the tree are dark against the sky.
Consider them as so many dark rivers, to be laid down in a map with absolute accuracy.
Without the least thought about the roundness of the stems, map them all out in flat shade, scrawling them in with pencil.
Then correct and alter them, rubbing out and out again, never minding how much your paper is dirtied.
(Only not destroying its surface.)
Correct until every bough is exactly, or as near as your utmost power can bring it, right in curvature and in thickness.
Look at the white interstices between the boughs with as much scrupulousness as if they were little estates which you had to survey, and draw maps of, for some important lawsuit, involving heavy penalties if you cut the least bit of a corner off any of them, or gave the hedge anywhere too deep a curve.
Try continually to fancy the whole tree nothing but a flat ramification on a white ground.
Do not take any trouble about the little twigs, which look like a confused network or mist.
Leave them all out, drawing only the main branches as far as you can see them distinctly.
Your object at present being not to draw a tree, but to learn how to do so.
When you have got the thing as nearly right as you can, take your pen, and put a fine outline to all the boughs.
Take care to put the outline within the edge of the shade, so as not to make the boughs thicker.
(The main use of the outline is to affirm the whole more clearly; to do away with little accidental roughnesses and excrescences.)
(It may perfectly well happen that in Nature it should be less distinct than your outline will make it; but it is better in this kind of sketch to mark the facts clearly.)
The temptation is always to be slovenly and careless.
The outline is like a bridle, and forces our indolence into attention and precision.
You cannot do too many studies of this kind.
Every one will give you some new notion about trees.
Biblioklept 