Modern Painters (vol. iii.),
and now here repeated, Fig. 3, will clearly enough {53} show the opposition
between this vertebrate form, branching again usually at the edges, _a_,
and the softly opening lines diffused at the stem, and gathered at the
point of the leaf _b_, which, as you almost without doubt know already are
characteristic of a vast group of plants, including especially all the
lilies, grasses, and palms, which for the most part are the signs of local
or temporary moisture in hot countries;--local, as of fountains and
streams; temporary, as of rain or inundation.

But temporary, still more definitely in the day, than in the year. When you
go out, delighted, into the dew of the morning, have you ever considered
why it is so rich upon the grass;--why it is _not_ upon the trees? It _is_
partly on the trees, but yet your memory of it will be always chiefly of
its gleam upon the lawn. On many {54} trees you will find there is none at
all. I cannot follow out here the many inquiries connected with this
subject, but, broadly, remember the branched trees are fed chiefly by
rain,--the unbranched ones by dew, visible or invisible; that is to say, at
all events by moisture which they can gather for themselves out of the air;
or else by streams and springs. Hence the division of the verse of the song
of Moses: "My doctrine shall drop as the rain; my speech shall distil as
the dew: as the _small_ rain upon the tender _herb_, and as the showers
upon the grass."

23. Next, examining the direction of the veins in the leaf of the alisma,
_b_, Fig. 3, you see they all open widely, as soon as they can, towards the
thick part of the leaf; and then taper, apparently with reluctance, pushing
each other outwards, to the point. If the leaf were a lake of the same
shape, and its stem the entering river, the lines of the currents passing
through it would, I believe, be nearly the same as that of the veins in the
aquatic leaf. I have not examined the fluid law accurately, and I do not
suppose there is more real correspondence than may be caused by the leaf's
expanding in every permitted direction, as the water would, with all the
speed it can; but the resemblance is so close as to enable you to fasten
the relation of the unbranched leaves to streams more distinctly in your
mind,--just as the toss of the palm leaves from their stem may, I think, in
their likeness to the springing of a fountain, remind you of their relation
to the des