to be found on wet rocks in scattered districts of Canada and the States
adjoining Canada. Surrounding its pretty violet flowers, of funnel
shape, are gummy leaves which close upon their all too trusting guests,
but with less expertness than the sun-dew's. The butterwort is but a
'prentice hand in the art of murder, and its intended victims often
manage to get away from it. Built on a very different model is the
bladderwort, busy in stagnant ponds near the sea coast from Nova Scotia
to Texas. Its little white spongy bladders, about a tenth of an inch
across, encircle the flowering stem by scores. From each bladder a bunch
of twelve or fifteen hairy prongs protrude, giving the structure no
slight resemblance to an insect form. These prongs hide a valve which,
as many an unhappy little swimmer can attest, opens inward easily
enough, but opens outward never. As in the case of its cousinry a-land,
the bladderwort at its leisure dines upon its prey.
[Illustration: Venus' Fly Trap--Open with a Welcome]
In marshy places near the mouth of the Cape Fear River, in the vicinity
of Wilmington, North Carolina, grows the Venus' fly-trap, most wonderful
of all the death-dealers of vegetation. Like much else in nature's
handiwork this plant might well have given inventors a hint worth
taking. The hairy fringes of its leaves are as responsive to a touch
from moth or fly as the sensitive plant itself. And he must be either a
very small or a particularly sturdy little captive that can escape
through the sharp opposed teeth of its formidable snare. It is one of
the unexplained puzzles of plant life that the Venus' fly-trap, so
marvellous in its ingenuity, should not only be confined to a single
district, but should seem to be losing its hold of even that small
kingdom. Of still another type is the pitcher plant, or side-saddle
flower, which flaunts its deep purple petals in June in many a peat-bog
from Canada southward to Louisiana and Florida. Its leaves develop
themselves into lidded cups, half-filled with sweetish juice, which
first lures a fly or ant, then makes him tipsy, and then despatches him.
The broth resulting is both meat and drink to the plant, serving as a
store and reservoir against times of drought and scarcity.
[Illustration: Shut for Slaughter]
Now the question is, How came about this strange and somewhat horrid
means of livelihood? How did plants of so diverse families turn the
tables on the insect world, and learn to eat instead of being themselves
devoured? A beginner in the builder's art finds it much 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 and there
deepens into green of the richest--a plain token of moisture in the
hollows--a blessing indeed in this dry weather. In the far West and
Northwest the buffalo grass has often to contend with drought for months
together, so that it has learned to strike deep in quest of water to
quench its thirst. It is a by-word among the ranchmen that the roots go
clear through the earth and are clinched as they sprout from the ground
in China. Joking apart, they have been found sixty-eight feet below the
surface of the prairie, and often in especially dry seasons cattle would
perish were not these faithful little well-diggers and pumpers
constantly at work for them. In the river valleys of Arizona although
the air is dry the subsoil water is near the surface of the ground. Here
flourishes the mesquit tree, _Prosopis juliflora_, with a tale to tell
well worth knowing. When a mesquit seems stunted, it is because its
strength is withdrawn for the task of delving to find water; where a
tree grows tall with goodly branches, it betokens success in reaching
moisture close at hand. Thus in shrewdly reading the landscape a
prospector can choose the spot where with least trouble he can sink his
well. And plants discover provender in the soil as well as drink. Nearer
home than Arizona we have only to dislodge a beach pea from the ground
to see how far in search of food its roots have dug amid barren stones
and pebbles. Often one finds a plant hardly a foot high with roots
extending eight feet from its stem.
And beyond the beaches where the beach peas dig so diligently are the
seaweeds--with a talent for picking and choosing all their own. Dr.
Julius Sachs, a leading German botanist, believes that the parts of
plants owe their form, as crystals do, to their peculiarities of
substance; that just as salt crystallizes in one shape and sugar in
another, so a seaweed or a tulip is moulded by the character of its
juices. Something certainly of the crystal's faculty for picking out
particles akin to itself, and building with them, is shown by the kelp
which attracts from the ocean both iodine and bromine--often dissolved
though they are in a million times their bulk of sea water. This trait
of choosing this or that dish from the feast afforded by sea or soil or
air is not peculiar to the seaweeds; every plant displays it. Beech
trees love to grow on limestone and thus declare to the explorer the
limestone ridge he seeks. In the Horn silver mine, of Utah, the zinc
mingled with the silver ore is betrayed by the abundance of the zinc
violet, a delicate and beautiful cousin of the pansy. In Germany this
little flower is admittedly a signal of zinc in the earth, and zinc is
found in its juices. The late Mr. William Dorn, of South Carolina, had
faith in a bush, of unrecorded name, as betokening gold-bearing veins
beneath it. That his faith was not without foundation is proved by the
large fortune he won as a gold miner in the Blue Ridge country--his
guide the bush aforesaid. Mr. Rossiter W. Raymond, the eminent mining
engineer of New York, has given some attention to this matter of
"indicative plants." He is of the opinion that its unwritten lore among
practical miners, prospectors, hunters, and Indians is well worth
sifting. Their observations, often faulty, may occasionally be sound and
valuable enough richly to repay the trouble of separating truth from
error. When we see how important as signs of water many plants can be,
why may we not find other plants denoting the minerals which they
especially relish as food or condiment?
Of more account than gold or silver are the harvests of wheat and corn
that ripen in our fields. There the special appetites of plants have
much more than merely curious interest for the farmer. He knows full
well that his land is but a larder which serves him best when not part
but all its stores are in demand. Hence his crop "rotation," his
succession of wheat to clover, of grass to both. Were he to grow barley
every year he would soon find his soil bared of all the food that barley
asks, while fare for peas or clover stood scarcely broached. If he
insists on planting barley always, then he must perforce restore to the
land the food for barley constantly withdrawn.
[Illustration: Maple Seed, with pair of wings]
A plant may diligently find food and drink, pour forth delicious nectar,
array itself with flowers as gayly as it can, and still behold its work
unfinished. Its seed may be produced in plenty, and although as far as
that goes it is well, it is not enough. Of what avail is all this seed
if it falls as it ripens upon soil already overcrowded with its kind?
Hence the vigorous emigration policy to be observed in plants of every
name. Hence the fluffy sails set to catch the passing breeze by the
dandelion, the thistle and by many more, including the southern plant of
snowy wealth whose wings are cotton. With the same intent of seeking new
fields are the hooks of the burdock, the unicorn plant, and the
bur-parsley which impress as carriers the sheep and cattle upon a
thousand hills. The Touch-me-not and the herb Robert adopt a different
plan, and convert their seed-cases into pistols for the firing of seeds
at as wide range as twenty feet or more. The maple, the ash, the
hornbeam, the elm and the birch have yet another method of escape from
the home acre. Their seeds are winged, and torn off in a gale are
frequently borne two hundred yards away. And stronger wings than these
are plied in the cherry tree's service. The birds bide the time when a
blush upon the fruit betrays its ripeness. Then the cherries are
greedily devoured, and their seed, preserved from digestion in their
stony cases are borne over hill, dale, and river to some islet or
brookside where a sprouting cherry plant will be free from the stifling
rivalries suffered by its parent. Yoked in harness with sheep, ox, and
bird as planter is yonder nimble squirrel. We need not begrudge him the
store of nuts he hides. He will forget some of them, he will be
prevented by fright or frost from nibbling yet more, and so without
intending it he will ensure for others and himself a sure succession of
acorns and butternuts.
Very singular are the seeds that have come to resemble beetles; among
these may be mentioned the seeds of the castor-oil plant and of the
_Iatropha_. The pod of the _Biserrula_ looks like a worm, and a worm
half-coiled might well have served as a model for the mimicry of the
_Scorpiurus vermiculata_. All these are much more likely to enlist the
services of birds than if their resemblances to insects were less
striking.
Nature elsewhere rich in hints to the gardener and the farmer is not
silent here. A lesson plainly taught in all this apparatus for the
dispersal of seeds is that the more various the planting the fuller the
harvest. Now that from the wheat fields comes a cry of disappearing
gains, it is time to heed the story told in the unbroken prairie that
diversity in sowing means wealth in reaping.
In a field of growing flax we can find--somewhat oftener than the farmer
likes--a curious tribe of plants, the dodders. Their stems are thin and
wiry, and their small white flowers, globular in shape, make the azure
blossoms of the flax all the lovelier by contrast. As their cousins the
morning glories are to this day, the dodders in their first estate were
true climbers. Even now they begin life in an honest kind of way with
roots of their own that go forth as roots should, seeking food where it
is to be found in the soil. But if we pull up one of these little
club-shaped roots we shall see that it has gone to work feebly and
doubtfully; it seems to have a skulking expectation of dinner without
having to dig and delve for it in the rough dirty ground. Nor is this
expectation unfounded. Watch the stem of a sister dodder as it rises
from the earth day by day, and it will be observed to clasp a stalk of
flax very tightly; so tightly that its suckers will absorb the juices of
its unhappy host. When, so very easily, it can regale itself with food
ready to hand why should it take the trouble to drudge for a living?
Like many another pauper demoralized by being fed in idleness, the plant
now abandons honest toil, its roots from lack of exercise wither away,
and for good and all it ceases to claim any independence whatever.
Indeed, so deep is the dodder's degradation that if it cannot find a
stem of flax, or hop, or other plant whereon to climb and thrive, it
will simply shrivel and die rather than resume habits of industry so
long renounced as to be at last forgotten.
Like the lowly dodder the mistletoe is a climber that has discovered
large opportunities of theft in ascending the stem of a supporting
plant. On this continent the mistletoe scales a wide variety of trees
and shrubs, preferring poplars and apple trees, where these are to be
had. Its extremely slender stem, its meagre leaves, its small flowers,
greenish and leathery, are all eloquent as to the loss of strength and
beauty inevitable to a parasite. Rising as this singular plant does out
of the branches of another with a distinct life all its own, it is no
other than a natural graft, and it is very probable that from the hint
it so unmistakably gives the first gardeners were not slow to adopt
grafts artificial--among the resources which have most enriched and
diversified both flowers and fruits. The dodders and mistletoes rob
juices from the stem and branches of their unfortunate hosts; more
numerous still are the unbidden guests that fasten themselves upon the
roots of their prey. The broom-rape, a comparatively recent immigrant
from Europe, lays hold of the roots of thyme in preference to other
place of entertainment; the Yellow Rattle, the Lousewort, and many more
attach themselves to the roots of grasses--frequently with a serious
curtailment of crop.
Yet in this very department of hers Nature has for ages hidden away what
has been disclosed within twenty years as one of her least suspected
marvels. It is no other than that certain parasites of field and meadow
so far from being hurtful, are well worth cultivating for the good they
do. For a long time the men who devoted themselves to the study of peas,
beans, clovers, and other plants of the pulse family, were confronted
with a riddle they could not solve. These plants all manage to enrich
themselves with compounds of nitrogen, which make them particularly
valuable as food, and these compounds often exist in a degree far
exceeding the rate at which their nitrogen comes out of the soil. And
this while they have no direct means of seizing upon the nitrogen
contained in its great reservoir--the atmosphere. Upon certain roots of
beans and peas it was noted that there were little round excrescences
about the size of a small pin's head. These excrescences on examination
with a microscope proved to be swarming with bacteria of minute
dimensions. Further investigation abundantly showed that these little
guests paid a handsome price for their board and lodging--while they
subsisted in part on the juices of their host they passed into the bean
or pea certain valuable compounds of nitrogen which they built from
common air. At the Columbian Exposition, of 1893, one of the striking
exhibits in the Agricultural Building set this forth in detail. Vials
were shown containing these tiny subterranean aids to the farmer, and
large photographs showed in natural size the vast increase of crop due
to the farmer's taking bacteria into partnership. To-day these little
organisms are cultivated of set purpose, and quest is being made for
similar bacteria suitable to be harnessed in producing wheat, corn, and
other harvests.
These are times when men of science are discontented with mere
observation. They wish to pass from watching things as nature presents
them to putting them into relations wholly new. In 1866 DeBary, a close
observer of lichens, felt confident that a lichen was not the simple
growth it seems, but a combination of fungus and algae. This opinion, so
much opposed to honoured tradition, was scouted, but not for long.
Before many months had passed Stahl took known algae, and upon them sowed
a known fungus, the result was a known lichen! The fungus turns out to
be no other than a slave-driver that captures algae in colonies and makes
them work for him. He is, however, a slave-driver of an intelligent
sort; his captives thrive under his mastery, and increase more rapidly
for the healthy exercise he insists that they shall take.
It is an afternoon in August and the sultry air compels us to take
shelter in a grove of swaying maples. Beneath their shade every square
yard of ground bears a score of infant trees, very few of them as much
as a foot in stature. How vain their expectation of one day enjoying an
ample spread of branch and root, of rising to the free sunshine of upper
air! The scene, with its quivering rounds of sunlight, seems peace
itself, but the seeming is only a mask for war as unrelenting as that
of weaponed armies. For every ray of the sunbeam, for every atom of
food, for every inch of standing room, there is deadly rivalry. To begin
the fight is vastly easier than to maintain it, and not one in a hundred
of these bantlings will ever know maturity. We have only to do what
Darwin did--count the plants that throng a foot of sod in spring, count
them again in summer, and at the summer's end, to find how great the
inexorable carnage in this unseen combat, how few its survivors. So hard
here is the fight for a foothold, for daily bread, that the playfulness
inborn in every healthy plant can peep out but timidly and seldom. But
when strife is exchanged for peace, when a plant is once safely
sheltered behind a garden fence, then the struggles of the battlefield
give place to the diversions of the garrison--diversions not
infrequently hilarious enough. Now food abounds and superabounds;
henceforth neither drought nor deluge can work their evil will; insect
foes, as well as may be, are kept at bay; there is room in plenty
instead of dismal overcrowding. The grateful plant repays the care
bestowed upon it by bursting into a sportiveness unsuspected, and indeed
impossible, amidst the alarms and frays incessant in the wilderness. It
departs from parental habits in most astonishing fashion, puts forth
blossoms of fresh grace of form, of new dyes, of doubled magnitude. The
gardener's opportunity has come. He can seize upon such of these
"sports" as he chooses and make them the confirmed habits of his wards.
Take a stroll through his parterres and greenhouses, where side by side
he shows you pansies of myriad tints and the modest little wild violets
of kindred to the pansies' ancestral stock. Let him contrast for you
roses, asters, tuberous begonias, hollyhocks, dahlias, pelargoniums,
before cultivation and since. Were wild flowers clay, were the gardener
both painter and sculptor, he could not have wrought marvels more
glorious than these. In a few years the brethren of his guild have
brought about a revolution for which, if possible at all to her, nature
in the open fields would ask long centuries. And the gardener's
experiments with these strange children of his have all the charm of
surprise. No passive chooser is he of "sports" of promise, but an active
matchmaker between flowers often brought together from realms as far
apart as France and China. Sometimes his experiment is an instant
success. Mr. William Paul, a famous creator of splendid flowers, tells
us that at a time when climbing roses were either white or yellow, he
thought he would like to produce one of bright dark colour. Accordingly
he mated the Rose Athelin, of vivid crimson, with Russelliana, a hardy
climber, and lo, the flower he had imagined and longed for stood
revealed! But this hitting the mark at the first shot is uncommon good
fortune with the gardener. No experience with primrose or chrysanthemum
is long and varied enough to tell him how the crossing of two different
stocks will issue. A rose which season after season opposes only
indifference to all his pains may be secretly gathering strength for a
bound beyond its ancestral paths which will carry it much farther than
his hopes, or, perhaps, his wishes.
Most flowers are admired for their own sweet sake, but who thinks less
of an apple or cherry blossom because it bears in its beauty the promise
of delicious fruit? Put a red Astrachan beside a sorry crab, a Bartlett
pear next a tough, diminutive wild pear such as it is descended from, an
ear of milky corn in contrast with an ear one-fourth its size, each
grain of which, small and dry, is wrapped in a sheath by itself; and
rejoice that fruits and grains as well as flowers can learn new lessons
and remember them. At Concord, Massachusetts, in an honoured old age,
dwells Mr. Ephraim W. Bull. In his garden he delights to show the mother
vine of the Concord grape which he developed from a native wild grape
planted as long ago as 1843. Another "sport" of great value was the
nectarine, which was seized upon as it made its appearance on a peach
bough. Throughout America are scattered experiment stations, part of
whose business it is to provoke fresh varieties of wheat, or corn, or
other useful plant, and make permanent such of them as show special
richness of yield; earliness in ripening; stoutness of resistance to
Jack Frost, or blight, or insect pests. Suppose that dire disaster
swept from off the earth every cereal used as food. Professor Goodale,
Professor Asa Gray's successor at Harvard University, has so much
confidence in the experiment stations of America that he deems them well
able to repair the loss we have imagined; within fifty years, he thinks,
from plants now uncultivated the task could be accomplished. Among the
men who have best served the world by hastening nature's steps in the
improvement of flowers and fruits, stands Mr. Vilmorin, of Paris. He it
was who in creating the sugar beet laid the foundation for one of the
chief industries of our time. One of his rules is to select at first not
the plant which varies most in the direction he wishes, but the plant
that varies most in any direction whatever. From it, from the
instability of its very fibres, its utter forgetfulness of ancestral
traditions, he finds it easiest in the long run to obtain and to
establish the character he seeks of sweetness, or size, or colour.