FLOWERS
Man's ideas of the use of flowers--Sprengel's great
discovery--Insects, not man, consulted--Pollen carried to
set seed--Flowers and insects of the Whinstone Age--Coal
Age flowers--Monkey-puzzle times--Chalk flowers--Wind-blown
pollen--Extravagant expenditure of pollen in them--Flower of
the pine--Exploding flowers--Brilliant alpines--Intense life in
flowers--Colour contrasts--Lost bees--Evening flowers--Humming
birds and sunbirds--Kangaroo--Floral clocks--Ages of
flowers--How to get flowers all the year round--Ingenious
contrivances--Yucca and fig--Horrible-smelling flowers--Artistic
tastes of birds, insects, and man.
For many centuries flowers were considered as pleasing and attractive
decorations stuck about the world in the same way as they are put in
a drawing-room in order to give people pleasure. Very soon they were
found to be extremely useful in poetry, sometimes to point a moral
or disguise a sermon, like the primrose in _Peter Bell_, but more
generally to produce a good impression on the BELOVED OBJECT. Burns
puts the usual view of flowers very nicely in the following: "But I
will down yon river rove amang the woods sae green, and a' to pu' a
posie to my ain dear May." Possibly this is the meaning also in the
exquisite lines of Shakespeare about the pansy:--
"Yet marked I where the bolt of Cupid fell:
It fell upon a little western flower,--
Before milk-white, now purple with love's wound,--
And maidens call it, love-in-idleness."
Even if there is no particular meaning, the "little western flower"
gives point and beauty to the lines.
People only began to understand flowers about the year 1793, when
Christian Conrad Sprengel, Rector of Spandau, near Berlin, published
a very interesting work. He had discovered that the beauty of
flowers and their colour and shape were by no means intended solely
to please _human_ eyes, but that they were designed to attract and
allure the eyes of _insects_. Before his time there had been many
guesses. Indeed, Theophrastus (born 371 B.C., and often mentioned in
this work) seems to have quite well understood why flowers produce
pollen, and that the fruit would not set and form seed unless pollen
was carried to the female part of the flower. He mentions that the
Pistacio has both male and female plants, and that Palms only form
dates when the pollen is carried to the female tree. This experiment
with the Date-palm was tried in 1592 by an Italian (Alpino) in an
Egyptian tour, and the Englishman, Jacob Bobart, the Pole, Adam
Zaluzianski (the latter in the same year) confirmed the general idea.
Then in the year 1694 Rudolp Jacob Camerarius, a German, carried on
a few more experiments, but no real definite advance was made until
1793, in the very midst of the French Revolution.[25]
[25] The historical account by Bonnier, _Cours de Botanique_, is
very interesting and complete.
The great point of Sprengel's discovery was in its being an
intelligible explanation of the reason why flowers have bright
colours, scent, and honey. At his time and indeed for many years
afterwards, botanists looked on the stamens, petals, and other
parts of the flower exactly in the way that a stamp collector looks
at punctures and postmarks, that is without thinking about their
meaning. Now we find that they are always designed to fulfil a
perfectly definite purpose, and that all their details are contrived
accordingly.
This purpose is to carry the pollen from the stamens of one flower
to the stigma of another. The pollen can usually be recognized as
a yellowish or reddish dust formed in the stamens; this dust is
generally rubbed off on an insect's proboscis or on part of its body.
When the insect reaches another flower the pollen is scraped off by
a sticky or gummy stigmatic surface. When the pollen has been placed
on this surface it grows, germinates, and part of it unites with the
egg-cell of the young seed.
The latter is then, and not till then, able to become ripe and
mature. It may be compared to cross-breeding in animals, though the
process does not exactly correspond.
But all flowers do not require insects to carry their pollen. In
early geological periods we do not find any flowers like those that
now exist, nor in those early times were there any flies, bees, or
butterflies.
The cockroach seems to have existed in Silurian (whinstone) times,
and many gigantic and extraordinary insects lived in those damp
forests of ferns, club-moss, and horsetails, of which the remains
now form our British coalfields. Mayflies, plantbugs, and especially
dragonflies (some of them with wings two feet across) existed, but
none of these insects are of much use as pollen-carriers.
Even much later on, when screw pines, monkey-puzzle trees, ginkgos,
and bamboos formed the forests and woods of Europe, crickets and
earwigs existed; but it is not until that geological period in which
the chalk was formed (the Cretaceous age) that fossil plants like
most of those now familiar to us occur. These had flowers intended
for insects, and with the fossil plants we find the fossils of the
insects that visited them. Bees, butterflies, and ordinary flies
appeared upon the scene just as soon as there were flowers ready for
them. Mr. Scudder has even found the fossils of certain plants, and
with them the fossils of butterflies closely allied to the present
butterflies which now live on present trees allied to those fossils!
How then was the pollen of the first flowers carried?
It was in all probability blown by the wind or carried in water.
Even now poplars, alders, birches, and oaks rely chiefly upon the
wind to carry their pollen. These plants were amongst the first of
our modern flora to appear upon the earth. Some of them possess very
neat contrivances suited to the wind. The catkins of the alder, for
example, hang downwards, so that each little male flower is protected
from rain by a little scale or bract above it. The pollen is very
light, dusty, or powdery, so as to fly a long distance. The Scotch
fir (_Pinus sylvestris_) has male flowers in little cones. These are
upright, and the pollen of each stamen drops on to a small hollow on
the top of the stamen below. It is then blown away by the wind on a
fine dry day, but it is not allowed to get out in wet weather. It is
said that vast clouds of pine pollen occur in America, and that the
water of certain lakes becomes quite yellow and discoloured by it at
certain seasons. Each little particle of pollen has two minute caps
or air-balloons which give it buoyancy, so that it can float easily
immense distances.
A curious little herb, the Wall Pellitory, and another foreign
species, the Artillery plant, produces small explosions of pollen.
When it is touched, there is a little puff or cloud of dusty pollen.
Even the common Nettle does the same on fine dry days when it is in
full flower.
But of course this carrying of pollen by the wind is a very
expensive arrangement. It is so much a matter of pure chance that
a grain arrives at its right destination. Suppose that a flower
is giving out clouds of pollen, then the chance of a pollen grain
reaching a female flower only five feet away is very small, even if
the stigma of the female flower is a quarter of an inch in diameter.
The chance of pollen reaching it will only be about 1 to 1440; 1439
pollen grains will be wasted[26] for every one that reaches the
stigma. But even this is not quite a fair calculation, for if the
female flower is not down wind, none will reach it at all!
[26] The pollen from the great pine forests of the Italian Alps
blown up to the snow becomes used in nourishing the Pink or
Red Snow Algæ, which colours it a delicate rose-pink. In lower
grounds all such pollen becomes, like leaf-mould, a manure for
other plants. There is no _waste_, strictly speaking.
But if an insect goes to the catkin of an alder or any other male
flower, it will see the red points of the stigma and will very likely
go there at once. This shows how much more reasonable and efficient
insects will be.
The immense majority of flowers are, in fact, purple, blue, red,
yellow, or white, so that they are conspicuous, and stand clearly
out against the green of their leaves. It is well known to all who
have arranged flowers for the table that the green of the leaves of
different plants varies greatly in its shade and tint. Many greens do
not match special flowers at all, but it is the fact that the green
of any one plant is always quite harmonious, and agrees well with its
own flowers!
Besides varied and beautiful colours, sweet or strong scents and
supplies of honey or nectar are provided for insects.
How did flowers manage to produce all these attractions? No one has
answered that question. We know in a general sort of way that the
parts of flowers are modified leaves, and that petals and stamens
become yellowish or pure white because they do not form green
colouring matter like ordinary leaves.
It is also known that on the Alps or on any high mountain, where the
air is pure and the sun strong, flowers become rich, brilliant, and
vivid. In such places as the "Jardin" near Mont Blanc, the pure,
deep, rich blue of gentians, the crimsons, reds, and purples of other
flowers, impress the most casual and unobservant traveller. "White
and red, yellow and blue, brown and green stand side by side on a
hand's breadth of space." In that strong mountain air, also, perfumes
are stronger, purer, and of finer quality than in the lowlands. There
is a more intense, active, and vigorous life going on in flowers than
is required by the more prosaic industries in other parts of a plant.
Flowers also often live at a higher temperature than the surrounding
air.
Kerner has described how the little flowers of Soldanella penetrate
the snow by actually melting a passage for themselves through it (see
p. 103).
This high temperature and vigorous life, shown also by the rapid
transpiration of flowers,[27] seems to hint that colours and perfumes
appear in consequence of rapid chemical transformations.[28]
[27] _Pharmaceutical Journal_, May 20th, 1899.
[28] Buscalioni e Traverso, _Atti del Ist. Bot. di Pavia_, vol.
10, 1904.
It was, of course, by degrees that the extraordinary variation
in colour, which exists in nature, came about. No doubt bees,
bumble-bees, wasps, and the more intelligent flies were improved and
developed æsthetically. We can almost tell by looking at a flower
what sort of insect probably visits it.
Not only so, but there are the neatest imaginable contrasts and
blends of colour. The common Bluebeard Salvia, e.g., has the
uppermost leaves (three-quarters to an inch long) of a deep, rich,
blue-purple, which the roving Bumble-bee will see from a long way
off. The Bumble-bee flies to this great splash of her favourite
hue and for a second buzzes angrily, then she notes the small
_bright-blue_ patches on the upper lips of the small flowers below
the leaves which are set off by _white_ hairs of the upper and
_yellow_ hairs of the lower lip.
That bees really do understand and are guided by colour may be
gathered from the following unfortunate accident. A certain hive
of bees which had been brought up in a blue-striped skep became
accidentally scattered. They tried to find their way back to their
old home, but many strayed, and it was noticed that they had tried to
enter the doors of every blue hive, which were strewn with the bodies
of the unfortunate intruders.[29]
[29] Von Buttel, _Respen_.
The rich blue-purple of Aconite, the dark strong red of the Woundwort
(_Stachys silvatica_) are specially beloved by bumble-bees and
hive-bees. Butterflies like any bright colour. Those flies which have
a long, sucking proboscis, resemble the bees in their tastes, but all
these insects are quite capable of finding out where they can get
honey most easily, and visit flowers whatever the colour may be.
A very strange and wonderful fact is that quite a number of plants
prefer the dark, or rather the dim, mysterious light of the gloaming.
Then the Honeysuckle, the Evening Campion, the Night-scented Stock,
Tobacco, and Schizopetalon give out their strongest scent and open
out their white flowers as widely as possible. That is because they
wish to attract the owlet moth and others which come out at this
time, when there are fewer enemies and more security. If you look
at any of these moth-flowers at mid-day, they are for the most part
closed up, they are not particularly attractive, and they are giving
out very little scent. The contrast to their condition in the evening
is most striking.
Not only insects but birds are used to carry pollen. The gorgeous
little humming birds, with their brilliant metallic crimson,
bronze-green, and purple, are of the greatest importance in the New
World. In the Old World they are replaced by the tiny _Nectarinidæ_
or Sunbirds, with breastplates almost as exquisitely jewelled. They
prefer the most gorgeous reds and scarlets, such as that of _Salvia
horminum_, _Lobelia cardinalis_, and the like. Fuchsias are regularly
visited by them in Tierra del Fuego, where sometimes they may be seen
busily at work during a shower of snow. In South Africa they seize
the stem of a Redhot Poker (_Tritoma_) (_Kniphofia macowanii_), and
twisting their little heads round, they suck the honey from every
blossom in succession. Still more interesting it is to see them
perched on the edge of one of those great tumbler-like heads of
Protea (e.g. _P. incompta_) and dipping their slender curved beaks
repeatedly into the flowers. Then the little male bird will alight
on a branch and make the most elaborate preparation for a song of
triumph. Although helped out by fluttering of wings and much display
of feathers and tail, the song is a very faint cheep of the feeblest
description, and very difficult to hear.
Not only birds but even animals are sometimes called into the
service. There is a group of small mammals which live on the honey of
flowers. Even the Kangaroo is said to occasionally take a draught of
nectar from some of the cup-like flowers of the Australian Dryandra
(_Proteaceae_).
But one of the most interesting and extraordinary facts is the
manner in which flowers fit in. They begin early in the morning: one
blossom opens out and then another; all endeavouring to catch the
attention of some passing insect. _Allionia violacea_ opens at three
or four a.m., and closes about eleven or twelve. Some wild Roses open
about four or five in the morning, as well as the Chicory, Roemeria,
etc. Virginian Spiderwort, Dandelion, and Nightshade are ready at
six in the morning. A great many (Buttercups, White Water Lily,
etc.) are open by seven a.m. Most of these early flowers are shut at
noon. Others begin to close about three or four in the afternoon.
The regular evening moth-flowers open about six p.m., though _Cactus
grandiflorus_ does not open till nine or ten p.m., and closes at
midnight.[30] Extraordinary as these variations seem, they are easily
explained. Some open early because there are then few competitors. By
far the greater number are open from nine a.m. till one or two p.m.,
because those hours are the favourite working time of most insects.
[30] Linnæus and many others have made Floral Clocks. Kerner,
_Natural History of Plants_, describes the opening and closing of
flowers very fully.
Flowers live for very different periods. That of the Wheat only lasts
for fifteen or twenty minutes (its pollen is carried by wind), and
is then over. There are others, Hibiscus and Calandrinia, which only
remain open for three or four hours, but a Foxglove will last six
days, a Cyclamen ten days, whilst Orchids may last for from thirty
to eighty days (_Cypripedium villosum_, seventy days, _Odontoglossum
Rossii_, eighty days).
Thus the sun every day through the summer, as he calls into life new
swarms of insects, sees at every hour of the day new flowers opening
their petals to his genial warmth and ready for the new bees and
flies. The development of the flower and that of its insect are
probably simultaneous, and equally regulated by the sun's warmth.
Moreover the opening periods do not merely fit in during the day, but
each flower has its own special month, and even in Scotland there is
no month in which some flower may not be found in bloom. Any stray
wandering insect can get its draught of honey at any season of the
year.
This is a matter of some importance for those who keep bees, and
the following list may be of some use. _February_: _Crocus vernus_,
Snowdrop, Black Hellebore, and Hazel. _March_: The preceding, _Arabis
alpina_, Bulbocodium, _Cornus mascula_, _Helleborus foetidus_, Giant
Coltsfoot, Gooseberry, various species of Prunus and Pyrus, Willow.
_April_: The preceding as well as _Adonis vernalis_, _Barbarea
vulgaris_, _Brassica napus_.
It is not worth while noting those that bloom from May to September,
for there are hundreds of good bee-flowers in these months. In
_October_: Borage, Echium, Sunflowers, _Lycium europæum_, _Malope
grandiflora_, Catmint, Tobacco, Ocimum, Origanum, _Phacelia
tanacetifolia_, and others. Most of these last into November.[31]
In December and January very few plants are in bloom. The following
have been noted at Edinburgh Botanical Gardens: _Dondia epipactis_,
_Tussilago fragrans_, Snowdrop, _Geum aureum_, Hepatica, _Primula
acaulis_, _P. veris_, _Aubrietia deltoidea_, _Crocus imperati_, _C.
suaveolens_, _Erica herbacea alba_, Helleborus (3 species), _Polygala
chamaebuxus_, _Andromeda floribunda_; also Sir H. Maxwell[32]
mentions _Azara integrifolia_, _Hamamelis_ _arborea_, and
_Chimonanthus fragrans_. Of wild plants, Chickweed, Whin or Furze,
_Lamium purpureum_, and Dandelion can generally be found in the depth
of winter.
[31] Huck, _Unsere Honig u. Bienenpflanzen_. These are drawn up
for Germany, and cannot be warranted for this country.
[32] _Memories of the Months._
The contrivances which can be found in flowers, and by which the
insect is forced to enter exactly along the proper path, are endless.
Each flower has some little peculiarity of its own which can only
be understood by thoroughly examining the plant itself. It is not
therefore possible to do justice to the ingenuity of flowers in
a work of this sort. There are orchids which throw their insect
visitors into a bath of water, so that they have to crawl with wet
wings up a certain path where they touch the pollen masses and
stigma; others which hurl their pollen masses at the visitor. In the
Asclepiads a groove is provided into which the leg of the insect
slips, so that it has to struggle to get its foot out, and must
carry off the pollen masses, though it often fails and leaves its
leg behind. Some Arums and Aristolochias have large traps in which
they imprison the insects, and only let them go when they are sure
to be pollen-dusted. In one of these flowers there are transparent
spots on the large petal-prison, which so attract the insects that
they remain opposite them instead of flying out (just as flies do
on a window-pane). Salvia has a stamen which is like a see-saw on a
support; the bee has to lift up one end, which brings the other with
its pollen flat down on to its back. The Barberry has a sensitive
spot on its stamen; when the insect touches the spot, the stamen
springs up suddenly and showers pollen upon it. In Mimulus the two
flaps of the stigma close up as soon as they are touched, which will
be when they have scraped off any pollen; then when the creature
withdraws, covered with the flower's own pollen, none of this can be
left on its own stigma, as this is shut up.
But instead of reading, one should watch a bumble-bee visiting the
Foxglove flowers. The sight of her busily thrusting her great hairy
body into the bell, which almost exactly fits her shape, while she
gurgles with satisfaction, will teach the reader far more about
the romance of flowers than many pages of description. If he then
carefully examines the flower, he will see how the honey, the arched
converging stamens, and the style, are placed exactly in the right
place and where they will have the most effect.[33]
[33] Compare Shelley, who watched all day "the yellow bees in
the ivy bloom," but he "did not heed what things they be." Moreover,
though he appreciated the general spirit of the bee, it is very
unlikely that he saw any of them on the Ivy!
One orchid, _Angraecum sesquipedale_, has a spur eighteen inches
long, and the great Darwin suggested that there must be an insect
somewhere with a tube long enough to reach the honey. Such an insect,
a large moth, was actually brought home from Madagascar, the place
where this orchid occurs, after a lapse of many years!
Perhaps more remarkable than anything else are such cases as the
Yucca and the Yucca-moth or the Fig-wasp and the Fig.
The Yucca is a fine lily-like plant resembling the Aloes in general
appearance. A particular sort of moth lives entirely upon the Yucca.
When the flowers open, the mother-moth kneads up a ball of pollen and
places an egg inside. This ball she thrusts down the style into the
ovary of the flower. There a grub develops from the egg and eats the
pollen, yet some of this pollen fertilizes the young seeds. If Yuccas
died out the moth would be exterminated. If the moths were destroyed,
no Yuccas would ever set their seed!
The Fig has two sorts of flower. The one (caprifig) produces only
male or pollen-yielding flowers. The other is the true edible fig.
Inside the caprifig are the grubs of the fig-wasp, which rejoice in
the name of _Blastophaga grossorum_. When grown up these force their
way out of the caprifig and, flying to the true fig, the mother-wasp
lays her eggs in certain flowers which have been apparently
specially modified for the purpose. At the same time she covers the
ordinary flowers with pollen from the caprifig. Her progeny return
to the caprifig. Here again the future of a valuable fruit-tree
is absolutely bound up with the fortunes of a tiny and in no way
attractive wasp!
Another very remarkable case is that of those flowers (Stapelia,
etc.), which in colour and general marking closely resemble decaying
meat or other objectionable substances. Very often the smell of such
flowers is exceedingly strong, and resembles the ordinary smell of
putrid matter. In one case an artist employed to paint the flower had
to use a glass bell, which was put over it. He could only lift it for
a second or two at intervals in order to see the exact colour, before
the horrible odour obliged him to cover it over again. Blowflies and
others, which are in the habit of resorting to such substances, seek
out these flowers in great numbers and lay their eggs upon them. In
so doing they carry the pollen.
There are certain fungi which have quite as horrible a smell, and
some of them also resemble decaying animal matter. These are most
eagerly sought out by the same blow-and other flies (bright green
lucilias, yellow-brown scatophagas, bluebottles, etc.). But in the
case of these fungi it is the spores, not pollen, which is carried by
the insect.
The effect of this flowery sort of life is abundantly evident in
the structure of the insects themselves. Their mouth has been most
wonderfully modified into a complex sucking apparatus; their legs
have been transformed to act as pollen-carrying baskets, and the
habits and tastes of the insects have been modified in the most
extraordinary way.
Perhaps also the association of bright colours with a very pleasant
sensation--that of a full, satisfying meal--has raised the artistic
sensibilities of butterflies, sunbirds, humming birds, etc. For
certainly these flower-haunting birds and butterflies are remarkable
for their brilliant colouring. This has probably been brought about
by the preference of the females for the most brilliantly coloured
male butterflies and humming birds.
At any rate bright reds and blues are common to both bird or insect
and to the flowers that they frequent. But the most curious point of
this whole question lies in the fact that human beings of all grades,
South Sea Islanders, the Ancient Greeks, Peruvians, Japanese, Romans,
as well as the Parisians and Londoners of to-day, appreciate the
beauty of colouring and grace of form which are so obvious in the
world of flowers.
Yet man has had nothing whatever to do with the selection of either
these colours or shapes. Many of those which he considers most
precious (such as the weird, spotted, and outlandish Orchids of
Madagascar and South America) have very likely scarcely ever been
seen by man at all. It is to the artistic eye of the honey-bee,
bumble-bee, butterfly, and of the humming bird and sunbird, that we
owe these exquisite colours. The grace and beauty of outline probably
depend upon their perfect symmetry and on the perfect suitability of
every curve to its purpose.
Therefore it seems that the eyes of man, whether savage or civilized,
are pleased and comforted by these same colours that delight the
little brains of insects and birds.
This is indeed a mysterious fact.