(Apocynum androsaemifolium) Dogbane family
Flowers - Delicate pink, veined with a deeper shade, fragrant,
bell-shaped, about 1/3 in. across, borne in loose terminal cymes.
Calyx 5-parted; corolla of 5 spreading, recurved lobes united
into a tube; within the tube 5 tiny, triangular appendages
alternate
with stamens; the arrow-shaped anthers united around
the stigma and slightly adhering to it. Stem: 1 to 4 ft. high,
with forking, spreading, leafy branches. Leaves: Opposite,
entire-edged, broadly oval, narrow at base, paler, and more or
less hairy below. Fruit: Two pods about 4 in. long.
Preferred Habitat - Fields, thickets, beside roads, lanes, and
walls.
Flowering Season - June-July.
Distribution - Northern part of British Possessions south to
Georgia, westward to Nebraska.
Everywhere at the North we come across this interesting, rather
shrubby plant, with its pretty but inconspicuous little
rose-veined bells suggesting pink lilies-of-the-valley. Now that
we have learned to read the faces of flowers, as it were, we
instantly suspect by the color, fragrance, pathfinders, and
structure that these are artful wilers, intent on gaining ends of
their own through their insect admirers. What are they up to?
Let us watch. Bees, flies, moths, and butterflies, especially the
latter, hover near. Alighting, the butterfly visitor unrolls his
long tongue and inserts it where the five pink veins tell him to,
for five nectar-bearing glands stand in a ring around the base of
the pistil. Now, as he withdraws his slender tongue through one
of the V-shaped cavities that make a circle of traps, he may
count himself lucky to escape with no heavier toll imposed than
pollen cemented to it. This granular dust he is required to rub
off against the stigma of the next flower entered. Some bees,
too, have been taken with the dogbane's pollen cemented to their
tongues. But suppose a fly call upon this innocent-looking
blossom? His short tongue, as well as the butterfly's, is guided
into one of the V-shaped cavities after he has sipped; but,
getting wedged between the trap's horny teeth, the poor little
victim is held a prisoner there until he slowly dies of
starvation in sight of plenty. This is the penalty he must pay
for trespassing on the butterfly's preserves! The dogbane, which
is perfectly adapted to the butterfly, and dependent upon it for
help in producing fertile seed, ruthlessly destroys all poachers
that are not big or strong enough to jerk away from its vise-like
grasp. One often sees small flies and even moths dead and
dangling by the tongue from the wicked little charmers. If the
flower assimilated their dead bodies as the pitcher plant, for
example, does those of its victims, the fly's fate would seem
less cruel. To be killed by slow torture and dangled like a
scarecrow simply for pilfering a drop of nectar is surely an
execution of justice medieval in its severity.
In July the most splendid of our native beetles, the green dandy
(Eumolpus auratus) fastens itself to the dogbane's foliage in
numbers until often the leaves appear to be studded with these
brilliant little jewels. "It is not easy," says William Hamilton
Gibson, "to describe its burnished hue, which is either
shimmering green, or peacock blue, or purplish-green, or
refulgent ruby, according to the position in which it rests." But
it is not golden, as its specific name would imply. It confines
itself exclusively to the dogbane. To prevent capture, it has a
trick of drawing up its legs and rolling off into the grass its
body so cleverly matches.
>From the silky coma on which the small seeds float away from long
pods to found new colonies, from the opposite leaves, milky
juice, and certain structural resemblances in the flowers, one
might guess this plant belonged to the milkweed tribe. Formerly
it was so classed; and although the botanists have now removed
its family one step away, the milkweed butterflies, especially
the Monarch (Anosia plexippus), ignoring the arbitrary dividing
line of man, still includes the dogbane on its visiting list. We
know that this plant derived its name from the fact that it was
considered poisonous to dogs; and we also know that all the tribe
of milkweed butterflies are provided with protective secretions
which are distasteful to birds and predaceous insects, enjoying
their immunity from attack, it is thought, from the acrid,
poisonous character of the foliage on which the caterpillars
feed.
COMMON MIIKWEED or SILKWEED
(Asclepias Syriaca; A. cornuti of Gray) Milkweed family
Flowers - Dull pale greenish purple pink, or brownish pink, borne
on pedicels, in many flowered, broad umbels. Calyx inferior,
5-parted; corolla deeply 5-cleft, the segments turned backward.
Above them an erect, 5-parted crown, each part called a hood,
containing a nectary, and with a tooth on either side, and an
incurved horn projecting from within. Behind the crown the short,
stout stamens, united by their filaments in a tube, are inserted
on the corolla. Broad anthers united around a thick column of
pistils terminating in a large, sticky, 5-angled disk. The anther
sacs tipped with a winged membrane; a waxy, pear-shaped
pollen-mass in each sac connected with the stigma in pairs or
fours by a dark gland, and suspended by a stalk like a pair of
saddle-bags. Stem: Stout, leafy, usually unbranched, 3 to 5 ft.
high, juice milky. Leaves: Opposite, oblong, entire-edged smooth
above, hairy below, 4 to 9 in. long. Fruit: 2 thick, warty pods,
usually only one filled with compressed seeds attached to tufts
of silky, white, fluffy hairs.
Preferred Habitat - Fields and waste places, roadsides.
Flowering Season - June-September
Distribution - New Brunswick, far westward and southward to North
Carolina and Kansas.
After the orchids, no flowers show greater executive ability,
none have adopted more ingenious methods of compelling insects to
work for them than the milkweeds. Wonderfully have they perfected
their mechanism in every part until no member of the family even
attempts to fertilize itself; hence their triumphal, vigorous
march around the earth, the tribe numbering over nineteen hundred
species located chiefly in those tropical and warm, temperate
regions that teem with insect life.
Commonest of all with us is this rank weed, which possesses the
dignity of a rubber plant. Much more attractive to human eyes, at
least, than the dull, pale, brownish-pink umbels of flowers are
its exquisite silky seed-tufts. But not so with insects. Knowing
that the slightly fragrant blossoms are rich in nectar, bees,
wasps, flies, beetles, and butterflies come to feast. Now, the
visitor finding his alighting place slippery, his feet claw about
in all directions to secure a hold, just as it was planned they
should for in his struggles some of his feet must get caught in
the fine little clefts at the base of the flower. His efforts to
extricate his foot only draw it into a slot at the end of which
lies a little dark-brown body. In a newly opened flower five of
these little bodies may be seen between the horns of the crown,
at equal distances around it. This tiny brown excrescence is hard
and horny, with a notch in its face. It is continuous with and
forms the end of the slot in which the visitor's foot is caught.
Into this he must draw his foot or claw, and finding it rather
tightly held, must give a vigorous jerk to get it free. Attached
to either side of the little horny piece is a flattened yellow
pollen-mass, and so away he flies with a pair of these pollinia,
that look like tiny saddle-bags, dangling from his feet. One
might think that such rough handling as many insects must submit
to from flowers would discourage them from making any more
visits; but the desire for food is a mighty passion. While the
insect is flying off to another blossom, the stalk to which the
saddlebags are attached twists until it brings them together,
that, when his feet get caught in other slots, they may be in the
position to get broken off in his struggles for freedom precisely
where they will fertilize the stigmatic chambers. Now the visitor
flies away with the stalks alone sticking to his claws.
Bumblebees and hive-bees have been caught with a dozen
pollen-masses dangling from a single foot. Outrageous imposition!
Does this wonderful mechanism always work to perfection? Alas!
no. It is a common thing to find dead hive-bees and flies hanging
from the flowers. While still struggling to escape, the unhappy
victims will be attacked by ants, beetles, and spiders, or killed
by heavy showers. Larger and stronger insects than honeybees are
required to regularly effect pollination and free themselves,
especially when they are so unfortunate as to catch several feet
in the grooves. Doubtless it is the bumblebee that can transfer
pollen with impunity; but very many other insects, not perfectly
adapted to the flowers, occasionally benefit them. Among the
large butterflies the Papilios, which suck with their wings in
motion, are the most useful, because in using their legs to
offset the motion of their wings they rapidly repeat those
movements which are necessary to draw the pollinia from the
anther cells and insert them in the stigmatic chambers of other
flowers. "Large butterflies like Danais," says Professor
Robertson, "hold their wings still in sucking, spending more time
on an umbel, but generally carrying pollinia. Small butterflies
are worse than useless. They remain long on the umbels sucking,
but resting their feet superficially on the flowers.
Since several moths were found entrapped, pollination must often
be brought about by night-flying Lepidoptera. As a rule, Diptera
(flies) either do not transfer pollinia at all, or become
hopelessly entangled when they do. "Occasionally pollen-masses
are found on the tongues of insects, especially on those of bees
and wasps, which move about with their unruly member sticking
out. Probably no one has ever made the exhaustive and absorbingly
interesting study of the milkweeds that Professor Robertson has.
Better than any written description of the milkweed blossom's
mechanism is a simple experiment. If you have neither time nor
patience to sit in the hot sun, magnifying glass in hand, and
watch for an unwary insect to get caught, take an ordinary
housefly, and hold it by the wings so that it may claw at one of
the newly opened flowers from which no pollinia have been
removed. It tries frantically to hold on, and with a little
direction it may be led to catch its claws in the slots of the
flower. Now pull it gently away, and you will find a pair of
saddlebags slung over his foot by a slender curved stalk. If you
are rarely skilful, you may induce your fly to withdraw the
pollinia from all five slots on as many of his feet. And they are
not to be thrown or scraped off, let the fly try as hard as he
pleases. You may now invite the fly to take a walk on another
flower in which he will probably leave one or more pollinia in
its stigmatic cavities.
Dr. Kerner thought the milky juice in milkweed plants, especially
abundant in the uppermost leaves and stems, serves to protect the
flowers from useless crawling pilferers. He once started a number
of ants to climb up a milky stalk. When they neared the summit,
he noticed that at each movement the terminal hooks of their feet
cut through the tender epiderm, and from the little clefts the
milky juice began to flow, bedraggling their feet and the hind
part of their bodies. "The ants were much impeded in their
movements," he writes, "and in order to rid themselves of the
annoyance, drew their feet through their mouths. Their movements
however, which accompanied these efforts, simply resulted in
making fresh fissures and fresh discharges of milky juice, so
that the position of the ants became each moment worse and worse.
Many escaped by getting to the edge of a leaf and dropping to the
ground. Others tried this method of escape too late, for the air
soon hardened the milky juice into a tough brown substance, and
after this, all the strugglings of the ants to free themselves
from the viscid matter were in vain." Nature's methods of
preserving a flower's nectar for the insects that are especially
adapted to fertilize it, and of punishing all useless intruders,
often shock us yet justice is ever stern, ever kind in the
largest sense.
If the asclepias really do kill some insects with their juice,
others doubtless owe their lives to it. Among the "protected"
insects are the milkweed butterflies and their caterpillars,
which are provided with secretions that are distasteful to birds
and predaceous insects. "These acrid secretions are probably due
to the character of the plants upon which the caterpillars feed,"
says Dr. Holland, in his beautiful and invaluable "Butterfly
Book." "Enjoying on this account immunity from attack, they have
all, in the process of time, been mimicked by species in other
genera which have not the same immunity." "One cannot stay long
around a patch of milkweeds without seeing the monarch butterfly.
(Anosia plexippus), that splendid, bright, reddish-brown winged
fellow, the borders and veins broadly black, with two rows of
white spots on the outer borders and two rows of pale spots
across the tip of the fore wings. There is a black scent-pouch on
the hind wings. The caterpillar, which is bright yellow or
greenish yellow, banded with shining black, is furnished with
black fleshy 'horns' fore and aft."
Like the dandelion, thistle, and other triumphant strugglers for
survival, the milkweed sends its offspring adrift on the winds to
found fresh colonies afar. Children delight in making pompons for
their hats by removing the silky seed-tufts from pods before they
burst, and winding them, one by one, on slender stems with fine
thread. Hung in the sunshine, how charmingly fluffy and soft they
dry!
Among the comparatively few butterfly flowers - although, of
course, other insects not adapted to them are visitors - is the
PURPLE MILKWEED (A. purpurasceus), whose deep magenta umbels are
so conspicuous through the summer months. Hummingbirds
occasionally seek it too. From Eastern Massachusetts to Virginia,
and westward to the Mississippi, or beyond, it is to be found in
dry fields, woods, and thickets.
The SWAMP MILKWEED (A. incarnata), on the other hand, rears its
intense purplish-red or pinkish hoods in wet places. Its leaves
are lance-shaped or oblong-lanceolate, whereas the purple
milkweed's leaves are oblong or ovate-oblong. This is a smooth
plant; and a similar species once reckoned as a mere variety (A.
pulchra) is the HAIRY MILKWEED. It differs chiefly in having some
hairs on the under side of its leaves, and a great many hairs on
its stem. Both plants bear erect, rather slender, tapering pods.
The POKE or TALL MILKWEED (A. exaltata - A. phytolaecoides of
Gray) may attain a height of six feet if the moist soil in which
it grows be exactly to its liking. Drooping or spreading umbels
of flowers whose corolla segments are pale purplish green, and
whose crown is clear ivory white or pink, appear from June to
August from Maine to Georgia and far westward. Sometimes the
tapering oblong leaves may be nine inches long. The erect
seedpods are drawn out to an unusually long point.
One may always distinguish the low-growing FOUR-LEAVED MILKWEED
(A. quadrifolia) from its relatives of ranker growth by its
general air of refinement, as well as by the two pairs of thin,
tapering leaves that grow in an upright whorl near the middle of
the slender stem. Usually there are no leaves on the lower part.
Small terminal umbels of delicate pink and white fragrant
flowers, which appear from May till July, give place to very
narrow pointed pods in late summer. From Maine to Ontario
southward to North Carolina and Arkansas is its range, in woods
and thickets chiefly.
HEDGE or GREAT BINDWEED; WILD MORNING-GLORY; RUTLAND BEAUTY;
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