uch more gainful to
examine the masonry of foundations, the rearing of walls, the placing of
girders and joists, the springing of arches and buttresses, than to look
at a cathedral, a courthouse, or a bank, finished and in service. In
like manner a student of insect-eating plants tries to find their leaves
in the making, in all the various stages which bridge their common forms
with the shapes they assume when fully armed and busy. Availing himself
of the relapses into old habits which plants occasionally exhibit under
cultivation, Mr. Dickson has taught us much regarding the way the
pitcher plant of Australia, the _Cephalotus_, has come to be what it is.
He has arranged in a connected series all the forms of its leaf from
that of a normal leaf with a mere dimple in it, to the deeply pouched
and lidded pitcher ready for deceitful hospitalities. And similar
transformations have without doubt taken place in the pitcher plants of
America. Observers in the Cape of Good Hope have noted two plants
_Roridula dentata_ and _Biblys gigantea_, which are evidently following
in the footsteps of the sundews, and may be expected in the fulness of
years to be their equal partners in crime. But why need we wander so far
as South Africa to find the germs of this strange rapacity when we can
see at home a full dozen species of catch-fly, sedums, primulas, and
geraniums pouring out glutinous juices in which insects are entangled?
Let stress of hunger, long continued, force any of these to turn its
attention to the dietary thus proffered, and how soon might not the
plant find in felony the sustenance refused to honest toil?

But after all the plants that have meat for dinner are only a few. The
greater part of the vegetable kingdom draws its supplies from the air
and the soil. Those plants, and they are many, that derive their chief
nourishment from the atmosphere have a decidedly thin diet. Which of us
would thrive on milk at the rate of a pint to five hogsheads of water?
Such is the proportion in which air contains carbonic acid gas, the main
source of strength for many thousands of trees, shrubs, and other
plants. No wonder that they array themselves in so broad an expanse of
leafage. An elm with a spread of seventy feet is swaying in the summer
breeze at least five acres of foliage as its lungs and stomach. Beyond
the shade of elms and maples let us stroll past yonder stretch of
pasture and we shall notice how the grass in patches here a