Indeed, are they not all riddles? Where is the flower which even to
the most devoted of us has yet confided all its mysteries? In
comparison with the insight of the earlier botanists, we have surely
come much closer to the flowers, and they have imparted many of their
secrets to us. Through the inspired vision of Sprengel, Darwin, and
their followers we have learned something of their meaning, in
addition to the knowledge of their structure, which comprised the end
and aim of the study of those early scholars, Linnaeus, Lindley,
Jussieu, and De Candolle. To these and other eminent worthies in
botany we owe much of our knowledge of _how_ the flowers are made, and
of the classification based upon this structure, but if these great
savants had been asked, "You have shown us that it _is so_, but _why_
is it thus?" they could only have replied, "We know not; we only know
that an all-wise Providence has so ordained and created it."
Take this little collection, which I have here presented, of stamens
and petals selected at random from common blossoms. What inexplicable
riddles to the botanist of a hundred years ago, even of sixty years
ago! For not until that time was their significance fully understood;
and yet each of these presents but one of several equally puzzling
features in the same flowers from which they were taken.
In that first anther, for example, why those pores at the tip of the
cells, instead of the usual slits at the sides, and why that pair of
horns at the back? And the next one, with longer tubes, and the same
two horns besides! Then there is that queer specimen with flapping
ears--one of six from the barberry blossom; and the pointed,
arrow-headed individual with a long plume from its apex; and the
curved C-shaped specimen--one of a pair of twins which hide beneath
the hood of the sage blossom. The lily anther, which comes last, is
poised in the centre. Why? What puzzles to the mere botanist! for it
is because these eminent scholars _were mere_ botanists--students and
chroniclers of the structural facts of flowers--that this revelation
of the truth about these blossom features was withheld from them. It
was not until they had become philosophers and true seers, not until
they sought the divine significance, the reason, which lay behind or
beneath these facts, that the flowers disclosed their mysteries to
them.
Look at that random row of petals, too!--one with a peacock's eye, two
others with dark spots, and next the queer-fingered petal of the
mignonette, followed by one of that queer couple of the monk's-hood
blossom which no one ever sees unless he tears the flower hood to
pieces. We all know the nasturtium, but have we thought to ask it why
these petals have such a deep crimson or orange colored spot, and why
each one is so beautifully fringed at the edge of its stalk?
These are but a dozen of the millions of similar challenges, riddles,
puzzles, which the commonest flowers of field and garden present to
us; and yet we claim to "know" our nasturtium, our pink, our
monk's-hood larkspur, our daisy, and violet!
No; we must be _more_ than "botanists" before we can hope to
understand the flowers, with their endless, infinite variety of form,
color, and fragrance.
It was not until the flowers were studied in connection with the
insects which visit them that the true secret of these puzzling
features became suspected.
We all know, or should know, that the anther in flowers secretes and
releases the pollen. For years even the utility of this pollen was a
mystery. Not until the year 1682 was its purpose guessed, when
Nehemias Grew, an English botanist, discovered that unless its grains
reached the stigma in the flower no seed would be produced (Diagram
A). But the people refused to believe this, and it was not until
fifty years later that Grew's statement was fully accepted, and then
only because the great Linnaeus assured the world that it _was_ true.
But about fifty years later another botanist in Germany, Sprengel,
made the discovery that the flower could not be fertilized as these
botanists had claimed, that in many blossoms the pollen could not fall
on the stigma.
[Illustration: A]
[Illustration: B]
Sprengel knew that this pollen must reach the stigma, but showed that
in most flowers it could not do so by _itself_. He saw that insects
were always working in the flowers, and that their hairy bodies were
generally covered with pollen, and in this way pollen grains _were_
continually carried to the stigma, as they could easily be in these
two blossoms shown at Diagram B. Sprengel then announced to the world
his theory--the dawn of discovery, the beginning of the solution of
all these floral riddles. The _insect_ explained it all. The bright
colors and fragrance were intended to attract him, and the nectar to
reward him, and while thus sipping he conveyed the pollen to the
stigma and fertilized the flower.
[Illustration: C]
[Illustration: D]
But now Sprengel himself was met with most discouraging opposition to
his theory, showing that he had guessed but half the secret after all.
Flowers by the hundreds were brought to his notice, like that shown in
Diagram C, in which the insect could _not_ transfer the pollen from
anther to stigma, as the stigma is closed when the pollen is ripe, and
like that in Diagram D, which does not open until the pollen is shed.
For seventy years this astonishing fact puzzled the world, and was at
last solved by the great Darwin, who showed that nearly all flowers
shun their own pollen, and are so constructed, by thousands of
singular devices, that the _insect_ shall bring to each the _pollen of
another flower_ of the same species, and thus effect what is known as
_cross-fertilization_.
We must then look at all flowers as expressions of welcome to some
insect--day-flowering blossoms mostly to bees and butterflies, and
night-bloomers to moths. And not only expressions of welcome, but each
with some perfect little plan of its own to make this insect guest the
bearer of its pollen to the stigma of another flower of the same
species. And how endless are the plans and devices to insure this
beautiful scheme! Some flowers make it certain by keeping the stigma
closed tight until all its pollen is shed; others place the anther so
far away from the stigma as to make pollen contact impossible; others
actually imprison these pollen-bringing insects until they can send
them away with fresh pollen all over their bodies.
Take almost any flower we chance to meet, and it will show us a
mystery of form which the insect alone can explain.
Here is one, growing just outside my door--a blossom "known" even to
every child, and certainly to every reader of the "Round Table"--the
pretty bluets, or Houstonia, whose galaxy of white or blue stars tints
whole spring meadows like a light snowfall. We have "known" it all
our lives. Perhaps we may have chanced to observe that the flowers are
not all constructed alike, but the chances are that we have _seen_
them _all our lives_ without discovering this fact. If we pluck a few
from this dense cluster beside the path, we observe that the throat of
each is swollen larger than the tube beneath, and is almost closed by
four tiny yellow anthers (Fig. 1). The next and the next clump may
show us similar flowers; but after a little search we are sure of
finding a cluster in which a new form appears, as shown in Fig. 2, in
which the anthers at the opening are missing, and their place supplied
with a little forked stigma! The tube below is larger than the first
flower for about two-thirds its length, when it suddenly contracts,
and if we cut it open we find the four anthers secreted near the wide
base of the tube. What does it mean, this riddle of the bluets? For
hundreds of years it puzzled the early botanists, only finally to be
solved by Darwin. This is simply the little plan which the Houstonia
has perfected to insure its cross-fertilization by an insect, to
compel an insect to carry its pollen from one flower and deposit it
upon the stigma of another. Once realizing this as the secret, we can
readily see how perfectly the intention is fulfilled.
In order to make it clear I have drawn a progressive series of
pictures which hardly require description. The flowers are visited
by small bees, butterflies, and other insects. At the left is an
insect just alighting on a clump of the blossoms of the high-anther
form indicated below it. The black probe represents the insect's
tongue, which, as it seeks the nectar at the bottom of the tube, gets
dusted at its thickened top with the pollen from the anthers. We next
see the insect flying away, the probe beneath indicating the condition
of its tongue. It next alights on clump No. 2, in which the flowers
happen to be of the high-stigma form, as shown below. The tongue now
being inserted, brings the pollen against the high stigma, and
fertilizes the flower, while at the same time its tip comes in contact
with the low anthers, and gets pollen from them. We next see the
insect flying to clump No. 3, the condition of its tongue being shown
below. Clump No. 3 happens to be of the first low-stigma form of
flowers, and as the tongue is inserted the pollen at its tip is
carried directly to the low stigma, and _this_ flower is fertilized
from the pollen from the anthers on the same level in the previous
flower. And thus the riddle is solved by the insect. From clump to
clump he flies, and through his help each one of the pale blue blooms
is sure to get its food, each flower fertilized by the pollen of
another.
[Illustration: 1st Clump.--Flower enlarged. Insect's Tongue inserted.
Pollen high on Insect's Tongue after withdrawal from Blossom.
2d Clump.--Flower enlarged. Pollen thrust against high Stigma at top
and touching Pollen below.
Pollen at Base of Insect's Tongue after withdrawal from Blossom.