The Pere Gilpin had the kind of science I like in the study of Nature,--a little less observation than White of Selborne, but a little more poetry .-- Just think of applying the Linnaean system to an elm! Who cares how many stamens or pistils that little brown flower, which comes out before the leaf, may have to classify it by?
What we want is the meaning, the character, the expression of a tree, as a kind and as an individual.
There is a mother-idea in each particular kind of tree, which, if well marked, is probably embodied in the poetry of every language.
Take the oak, for instance, and we find it always standing as a type of strength and endurance.

I wonder if you ever thought of the single mark of supremacy which distinguishes this tree from all our other forest-trees?
All the rest of them shirk the work of resisting gravity; the oak alone defies it.

It chooses the horizontal direction for its limbs, so that their whole weight may tell,--and then stretches them out fifty or sixty feet, so that the strain may be mighty enough to be worth resisting.

You will find, that, in passing from the extreme downward droop of the branches of the weeping-willow to the extreme upward inclination of those of the poplar, they sweep nearly half a circle.

At 90 degrees the oak stops short; to slant upward another degree would mark infirmity of purpose; to bend downwards, weakness of organization.