The great Swedish botanist, Linnaeus, nearly two hundred years ago,
basing his classification of plants on their flowers, found it
necessary to name and account for all of the parts of a flower. In many
cases he found structures that were neither sepals, petals, stamens nor
pistils, and as these contained, or were wet with, a sweet fluid, he
gave this the fanciful name “nectar”--the drink of the gods, and called
the parts of the flower that produced or contained it, “nectaries.”
As these nectaries were different from stamens and pistils, which
Linnaeus recognized as the sexual organs of flowers, though they
are sometimes connected with them, and as they were different from
ordinary sepals and petals, though sometimes connected with them,
they presented something of a question to the men of that day, who
were curious to know what the parts of a plant really are and what
they do. For this reason the study of nectaries became something of
a popular diversion for a generation or two; and a general idea that
they are organs for secreting sugar became established; not necessarily
an idea of secretion, though, for just as animals excrete various
organic substances that are by-products, or waste, from some of their
functions, so it was thought by some students that the sugar or nectar
might really be an excreted waste or surplus rather than a substance
secreted because it is to become useful to the plant.
[Illustration: Fig. 98. Sprengel’s title page.
Das
entdeckte Geheimniſs
der
NATUR
im Bau und in der Befruchtung
der
Blumen
von
Christian Konrad Sprengel,
Mit 25 Kupfertafeln.
Berlin, 1793.
bei Friedrich Vieweg dem æltern.]
Toward the end of the eighteenth century a German rector, Sprengel,
who seems to have found in nature a good deal of inspiration that he
failed to “put over,” noticed that the petals of the common German
wild geranium were fringed with hairs at their bases. That was in the
day before men believed in evolution, but when they did believe in a
purposeful creation. Sprengel was convinced that an all-wise Creator
would not have made a single hair in vain, and he set about discovering
what these hairs were for, much as a sensible person, seeing the
governor on an engine today would try to find out what it is for. Below
the break between the petals, he found a nectar gland, producing its
sugary fluid; and he saw the hairs would prevent the nectar from being
diluted or washed away by rain or dew. This brought him back to the
original question--what nectaries and nectar are for. He got his answer
to this by watching the plant and seeing that bees visited the flowers
and removed the nectar as what might be called the raw materials of the
honey industry.
In Sprengel’s day the general impression was not only that things have
been created just as we find them, but created for our own ultimate
good. So Sprengel found an answer in discovering that the hair fringe
of the geranium petals protects the nectar of the flowers and so
preserves it for bees to use in manufacturing honey for our breakfast
table.
When you stop to think about it, Sprengel could hardly have had the
curiosity to study out his geranium question to an answer without
being spurred to look at other flowers to see if they might not have
something interesting of the same sort to offer. He yielded to the
impulse to look at other flowers, and he found his geranium to be a
very drab specimen compared with some of the irregular and painted
flowers that he studied out in the same way. He must have felt no
common pride when, in 1793, he published the results of his studies,
with simple but effective illustrations, under a title that meant
revealing to mankind the newly discovered secret of nature in the
structure and fertilization of flowers.
But Sprengel seems not to have been the sort of man to whom such an
answer really was an answer, and he looked further. It does not seem
to have taken him long to see that while gathering their own store
of honey, and obviously without consciousness that they were doing
anything else, the bees became dusted with pollen from geranium stamens
and rubbed it off on geranium stigmas while going their rounds of the
flowers. This conclusion evidently answered two questions--what the
hairs are for, and what nectar is for.
It is not necessary to walk down Michigan Boulevard on a windy day to
realize that we belong to an imitative race. The corner grocery and the
drug store show it as well as the windows of milliners and dressmakers,
shoe shops and news stands, or as the sights that issue from a barber
shop in a college town.
Fashions run in fads and interests quite as much as in dress. Linnaeus
was a great botanist; perhaps none has been greater. He not only
reduced a chaotic science to order, but interested men in its study to
a remarkable extent. It is rather unfairly charged against him that
because his service was somewhat one-sided, those whose interest he
awakened were extremely one-sided, in that they did not see or care for
much in botany beyond finding, describing and classifying new plants.
This was well enough worth doing; it is not finished yet, and will not
be finished for many years to come; but it had become so fascinating
and workable through the genius of the Swedish master that his
followers seized on it with eagerness, and it was a long time before a
mind of original habits and impulses broke loose from the train.
The man who possessed this originality was Darwin, the promulgator of
the now universally accepted idea of organic evolution. To him has been
ascribed the introduction of a new teleology into natural science,
recognizing that structures and functions are because they are or have
been of use--not of use to man necessarily, though man may turn them to
account--but to their possessor.
[Illustration: Fig. 99. Ant acacia.]
This was Sprengel’s conclusion as to the nectar of geranium flowers,
which he found led to their fertilization. The essential difference
between his way of seeing it and Darwin’s is that he thought the entire
mechanism has been specially made by the Creator as a means to an end,
while Darwin saw in it the gradual modification of earlier structures
because the new were helpful in the struggle of life and their
possessors for this reason were likely to survive and pass them on to
their offspring.
There is a German country saying that the honeybee was forbidden the
red clover because she didn’t keep Sunday. Beekeepers know that her
tongue is a little too short for the honey tube of the red clover
flower and that she doesn’t waste time in trying to get what is out
of her reach. They know, too, that some races of honeybees really can
suck the red clover nectar because they have longer tongues, and if
beekeepers ever want to do it they can probably set an expert plant
breeder to work at breeding a race of red clover with a tube short
enough so that even the German honeybee can get at its nectar. Natural
evolution hasn’t done this. Where red clover is at home bumblebees are
found, and bumblebees have no difficulty in reaching its nectar much as
hawk-moths get that of a moon flower, which is far beyond the reach of
any kind of bee. But in the South Seas, where there are no long-tongued
bees, red clover finds itself as unable to set seed as the German
honeybee is to get at its nectar. Bee and flower have evolved together,
where both are at home, into a harmony of structure that is helpful to
them both.
Nothing was more suggestive to Darwin in his search for evidences of
evolution, or modification through descent, than this sort of harmony
of structure and habit in flowers and insects; and one of his earliest
and most effective books in bringing his views to the comprehending
notice of others was one dealing with the mutual relations between
those freaks in flowers, the orchids, and their insect visitors.
For Sprengel’s teleology, Sprengel’s explanation of nectar as a means
of securing fertilization was sufficient. For Darwin’s teleology, it
carried another question: =Why?= The geranium flower has both stamens
and pistil, standing in its middle. The one might fertilize the other
just as well as not, apparently; and yet this does not happen, for
the pollen-bearing anthers of the stamens drop off before the stigmas
of the pistils come to maturity. The same thing may be seen on any
single-flowered geranium in a bay window or a greenhouse or a summer
window box or flower bed, only this geranium does not belong to the
genus =Geranium= of the botanists, but to the related African genus
=Pelargonium=.
Looking for a further reason, Darwin saw a step further into the
mystery when he found that these and many other flowers that ought to
get on without any help are as dependent upon insects through their
own failure to bring pollen and stigma together as those are in which
stamens and pistils are borne in separate flowers--often on separate
plants. To him, nectar and its attendants--flower fragrance, color,
variegation, bizarre shape, long tubes, nectar guards of hairs or some
other structure--meant what they had meant to Sprengel, fertilization
through insect aid; but they meant something more, fertilization of one
flower by pollen from another flower--crossing.
And still the questions multiply. Why do not all flowers have stamens
and pistil side by side? Why, when they have this structure, do
they not time the maturity of these essential parts so as to secure
effective functioning without all the nectar machinery? In other words,
=why= is crossing so commonly necessitated and provided for?
Science of every kind has been advanced by three methods--reasoning,
observation, experimentation. Sprengel’s answer was reached by the
first two; the new answer sought by Darwin was to be obtained through
the third. For eleven years he put the question direct to the plants
themselves, fertilizing them by their own pollen, crossing them,
raising and requestioning their offspring. More and stronger progeny
from crossing was the answer.
The popularity that Linnaeus had given to characterizing and
classifying living things, was transferred by Darwin to studying their
structure and doings. Sprengel’s idea fell upon barren soil; Darwin’s
was cultivated with care and skill.
Two men--Mueller, a German, and Delpino, an Italian, stand out most
prominently among a multitude who observed and wrote and pictured
the marvels of flower and insect harmonies for a generation. All did
excellent work in furnishing details and corroborations; but Darwin
had answered the question as to the what and the why of the nectar of
flowers.
But there is nectar that is not produced in flowers. Look at the
queer spots in the angles between the veins on the under side of a
catalpa leaf, when it is young; or at the little goblets on the stalk
of a cherry or peach or snowball leaf, or at the pin-head spots on a
trumpet-creeper or paeony calyx, and you may see glands there that
secrete a sweet fluid. Bees may not care for it, but wasps or ants do.
The cotton plant has such sweet nectar glands on the outside of the
cluster of bracts about each blossom, and on the back of its leaves.
In a very few cases such “extrafloral” nectar serves the same purpose
as that within the flowers; but generally it does not lead to
fertilization. Delpino called the nectar that leads to fertilization
“nuptial” nectar, and the other “extranuptial.”
In the seventies of the last century an English mining engineer,
Belt, well known in the ore regions of Colorado, was marooned by his
profession on a mining property in Nicaragua. Using his eyes took the
place with him of tennis, or of dissipation, which is the white man’s
bane in the tropics. He saw that a certain kind of ants cut the leaves
of trees into bits which they take into their nests, and that roses and
other introduced plants fared hard with these leaf cutters, unless they
were protected by aromatic oils, as various kinds of citrus leaves are,
or in some other way.
Belt did not fail to notice that ants visited extrafloral nectaries in
numbers. In the case of those on some acacias he found the ants very
pugnacious. I confess that in Guatemala I have preferred, myself, to
go around a bush or a grove of such acacias with their ant guards. As
with Sprengel’s geranium hairs, these nectaries unfolded question after
question.
In Belt’s case, the tips of the acacia leaflets ripen also into little
fruit-like bodies that the ants gather and take into their nests;
and they make these nests in the stipules that flank each leaf and
sometimes are shaped like a pair of small buffalo horns. It is an
interesting undertaking to get the ant census of an acacia twig of this
sort. The danger may not be as great, but it is as real and perhaps
as painful as in taking the census of a mountain valley noted for
moonshine traffic.
Belt drew the conclusion that extranuptial nectar, sometimes
supplemented by solid food and shelter, is of use to the plant that
provides it by maintaining a bodyguard of ants on plants that otherwise
would be defoliated and injured by leaf cutters or grazing animals,
much as Sprengel and Darwin found an explanation of nuptial nectar in
the benefit of insect pollinization of the flowers.
This is the simple story of nectar, simply told, as it has been
seen by observing and thinking men. But it is not a story free from
complications. Our blue violets rarely set fruit from their showy
nectar-bearing flowers, but their main reliance for seed is on
flowers produced below the leaves, and these do not open, but are
self-fertilized. The beautiful =Poinsettia=, with its brilliant red
bracts and large cups overflowing with thick nectar, does not fruit
in West Indian gardens any more than it does in our greenhouses at
Christmas time. And irresistibly pugnacious as the acacia ants are,
those that visit our paeonies and cassias and other plants do not
usually more than protest mildly if we molest the plants that they are
on.
Are the explanations of Sprengel and Darwin, and of Belt wrong? No
other that are at all satisfactory have been offered.
When one stops to think of it, the secretion of nectar is an unusual
phenomenon. Sugar is made within plants and it does not leak from them
unless they have been injured. The sugar beet takes various substances
out of the soil water, but it does not permit the passage of sugar
into the soil water. And yet nectar, essentially sugar, is passed out
of the plant, within which it was manufactured. This is because it is
secreted--or excreted--through specialized glands. Everyone who grows
plants in a bay window has seen young clover or grass leaves with a
drop of water on their tips at some time or other. A few grains of
bird seed in a flower pot covered by a pane of glass will show this as
quickly as the seedlings come up.
These drops pass out finally through pores; but they are drops of water
and not of nectar. If we can imagine a gland behind such a water pore,
secreting sugar--letting it really get out of the cells with or into
the water, we can picture a nectar gland. Such glands occur in some
flowers. Some botanists believe that extranuptial nectar glands were
originally water glands that have acquired the habit of secreting sugar.
This habit is a very unusual and a very peculiar one. It is not really
understood except as it may be connected with usefulness to the
plant. If this usefulness is not indirect, in the ways suggested by
Darwin and Belt or otherwise, it must be direct. Water glands relieve
over-pressure when absorption is high and evaporation low; in some of
the calla family the water even spurts from the tips of the leaves at
times. But sugar is not like water, taken in in quantity and to spare;
it is manufactured, and in the case of nectar glands it is manufactured
where it is secreted. Nobody has yet suggested any physiological
function of plants calling for sugar safety valves situated in
the queer positions occupied by extranuptial nectar glands, and no
satisfactory direct physiological explanation of the nuptial glands has
been suggested.
The actual status of nectar in botanical science is about this: When it
is produced in flowers, and in some cases when it is outside of them,
but near them, it demonstrably serves to secure cross-pollinization
through the aid of insects, or humming birds and their like, when
the flowers are long, tubular and red, as in the trumpet creeper,
the trumpet honeysuckle and the scarlet salvia. It is then “nuptial
nectar.” When it does not serve the plant in this way and so is
“extranuptial,” it occurs in the neighborhood of the flowers, as in
cotton, sweet potato, trumpet creeper and paeony, where it attracts
numbers of ants, which are often very pugnacious, and to the extent of
their activities it prevents injury to the flower buds and flowers,
especially in their early stages; or it occurs on developing leaves
during the period of their greatest need. More rarely, as in the
acacias, the leaves continue to secrete it through the season, so that
those that are mature add to the protection of the younger leaves and
the flowers and the young fruit.
That neither of these functions is served in exceptional cases, and
that some flowers rely on the wind for effective pollination, or have
lapsed into self-fertilization; or that really pugnacious ants do not
commonly frequent the extranuptial glands of most plants in temperate
regions, and that some plants get along very well without such help,
mark questions that will continue to stimulate observation and
experiment. But nothing now known of the physiology of plants offers
an alternative explanation for that which connects nectar with either
pollination or defense; and until such an explanation can be found
nectar will continue to be regarded as connected indirectly with these
services through insect or bird relations.--William Trelease, Botanist,
University of Illinois. American Bee Journal, Dec., 1919. (See also
Physiology of Nectar Secretion).
NEGUNDO, see Box Elder.
NEVADA--Honey Sources of.
Much of Nevada is mountain and desert country. Alfalfa is the principal
source of surplus honey, though sweet clover also yields. There are
numerous minor sources, as willows along the streams and many of the
desert plants.
NEW BRUNSWICK--Honey Sources of.
In New Brunswick the principal sources of nectar are alsike and white
clover, fireweed, goldenrod and aster. Willows and maples stimulate
early brood rearing.--F. W. L. Sladen.
NEW HAMPSHIRE--Honey Sources of.
The honey flora of New Hampshire is very similar to that of other
New England States. In spring, willows, maples, fruit blossoms and
dandelions keep the bees busy in preparation for the main flow, which
comes from the clovers. Goldenrod is also important. Sumac, laurel,
blueberries and asters are worthy of mention, also.
NEW JERSEY--Honey Sources of.
Plants from which nectar is gathered in less than surplus quantities:
Maples, mid-March-early April.
Peach early April.
Pear, mid-April.
Apple, late April early May.
Willows, late April.
Dandelion, early May.
Wild strawberry, May.
Lupine, May.
Raspberry, May.
Grape, late May-early June.
Huckleberry, blueberry, late May-late June.
Persimmon, mid-June-late June.
Vervain, late June-early September.
Virginia creeper, late June-late July.
Milkweed, silkweed, July.
False indigo, July.
Button bush, July.
Burdock, July-October.
Tree of Heaven, pride of China, July.
Catnip, July.
Motherwort, August.
Smartweed, heartsease, late August-mid-September.
Horsemint, August-September.
Boneset, mid-August-September.
Surplus honey plants:
Crimson clover, mid-May.
Locust, May 20-June 1.
Tulip-poplar, May 26-June 10.
Poison ivy, mid-May-mid-June.
Holly, late May-late June.
Mountain laurel, late May-late June.
Sheep laurel, late May-late June.
Swedish clover, alsike clover, June 1-July 10.
White clover, early June-mid-July.
Dogbane, Indian hemp, early June-late August.
Basswood, linden, late June-early July.
California privet, mid-July-late July.
Sumac, mid-June-mid-July.
White sweet clover, June-November.
Cranberry, June 15-August 15.
August flower, soap bush, sweet pepper bush, late July-late August.
Rose mallow, swamp mallow, late July-early September.
Burdock, July-November.
Spanish needle, mid-August into October.
Heartsease, smartweed or blackheart, August-September.
Heath aster, white aster or St. Michaelmas daisy, late
August-mid-October.
Bushy goldenrod, late August-mid-October.
Buckwheat, early August.