PLANTS SPREAD BY MEANS OF ROOTS.
3. Fairy rings.--Several low forms of plant life, such as _Marasmius
oreades_, _Spathularia flavida_, and some of the puffballs, start
in isolated spots in the grass of a lawn or pasture, and spread each
year from a few inches to a foot or more in every direction, usually
in the form of a circle; at the end of fifteen years some of these
circles acquire a diameter of fifteen to twenty feet or more. These
are known as fairy rings. Before science dispelled the illusion they
were believed to have been the work of witches, elves, or evil spirits,
from which arose the name.
Several kinds of lichens and mosses and the like, growing on the barks
of trees, fence boards, and low ground, spread slowly in the manner
of fairy rings.
However, the spreading is not always a slow, creeping process, for
sometimes these low plants spread over an incredible distance in a
short space of time. In some instances they appear suddenly almost
anywhere, and at any season of the year. They are all minute and exist
in countless numbers, and their devices for securing wide dispersion
are so various as to entitle them to first rank in this respect. Some
send off spores with a sharp puff, as if shot from a little gun. Some
of these spores float on water, and some are sticky and thus gain
free rides. It is not at all improbable that some are carried by the
winds across oceans and continents.
It is well known that many of the lower species of plants are more
widely distributed over the earth than most of the higher plants.
Every cloud from a ripe puffball consists of thousands of spores
started on the wings of the wind for an unknown journey. Their habits
are not past finding out, but to examine them a person needs a good
microscope. Most of them have no special common name, and with one
or two exceptions further mention of the mode of distribution of this
fascinating portion of plant life cannot here be made.
In our botanic garden was planted a patch six feet across of what
is known as Oswego tea, bee balm, or red-flowered bergamot, an
interesting plant with considerable beauty. It grew well for a year,
the next year it failed to some extent, and on the third most of the
plants died, or nearly died, excepting the spreading portion all
around the margin. This is a fairy ring of another type, and represents
a very slow mode of travel. As further illustrations of this topic
study common yarrow, betony, several mints, common iris, loosestrife,
coreopsis, gill-over-the-ground, several wild sunflowers,
horehound, and many other perennials that have grown for a long time
without transplanting.
The roots of plants are seldom much observed, because they are out
of sight. In soft ground the roots of the common or black locust extend
from twenty to forty feet in each direction, and almost anywhere along
these roots buds may appear, and a shoot spring up and become a tree.
This peculiarity is worth as much to locusts in the matter of spreading
as though the parent trees were able to move about. A number of kinds
of poplars and willows, ailanthus, some of the elms, ashes, sweet
potatoes, milkweeds, Canada thistles, and others behave in a similar
manner. Little bits of Canada-thistle root half an inch long may send
forth buds, and each bud grow to be an independent plant.
[Illustration: FIG. 1.--Buds and shoots sprouting from roots of the
common locust.]
Roots have a peculiarity not usually known. They stretch out and crook
about here and there, penetrating the crevices of the soil wherever
there is the least chance, and the matured portions begin to shorten,
reminding one somewhat of an angleworm when one end has been stepped
on. By this shortening process the top or crown of a dandelion or
plantain is pulled down beneath the surface of the ground.
4. How nature plants lilies.--Lilies grow from bulbs which are
planted six inches beneath the surface. Do you know how nature plants
them? A seed starts and becomes a small plant on the surface of the
leaf mould or a little beneath; little roots push downward and to
right and left; and later, after getting a good hold below with
numerous branchlets, the slender roots shorten and tug away at the
tiny bulb above, as much as to say, "Come down a little into mother
earth, for cold winter is approaching and there will be danger from
frost." The young bulb is drawn down an inch more or less, the slender
roots perish with the growing year, but the bulb is preserved. The
seedling was well planned; for while it had yet tender leaves during
its first year, starch and protoplasm were stored up in the thickened
scales of the bulb. During the second spring some of this food in
store is used to send down another set of slender roots with the
message to gather in more water, potash, phosphorus, nitrogen, and
other substances to help grow a larger bulb. In late summer and autumn
the new roots contract and pull away at the greater bulb, and down
it goes into the ground another inch or so. I have a theory as to
how it finally comes to be drawn down just deep enough and no more,
but I will not venture to give it. This process is repeated from year
to year till the proper depth is reached for preserving the full-grown
bulb. And this is the way nature plants bulbs.
In a similar manner young slender roots well anchored in the soil,
at or near the close of the growing season, pull downward and outward
large numbers of bulblets that form around a parent bulb of some kinds
of leeks, tulips, star-of-bethlehem, globe hyacinth, and monkshood.
The pull of the roots is much greater to one side than downward,
because most of the longest roots extend sidewise. Marilaun reports
that a certain lawn in Vienna was mown so frequently that tulips could
not go to seed, but after twenty years, from a very few bulbs planted
near each other, a space twenty paces in diameter was well covered
by tulips. And this is one way tulips travel, slow and sure.
5. Roots hold plants erect like ropes to a mast.--Did you ever lift
vines of cucumbers, squashes, and the like, where they had rooted
at the joints, and observe how forlorn they looked after the operation,
with leaves tipped over, unable to remain erect? While growing, the
stem zigzags or winds about more or less, and thus enables it to hold
the leaves erect; besides, the tendrils catch on to weeds and curl
up tight, and the roots at the joints are drawn taut on each side
after the manner mentioned above, and act like ropes to a mast to
hold the stem in its place, and thus help to hold the leaf above erect.
6. How oaks creep about and multiply.--Oaks come from acorns;
everybody knows that. The nuts are produced in abundance, and those
of the white oak send out pretty good tap roots on the same year they
fall. Some of the nuts roll down the knoll or are carried about by
squirrels or birds, as mentioned elsewhere. Let me tell you one thing
that I discovered the white oaks were doing in the sand of the
Jack-pine plains of Michigan. In dry weather the dead grass, sticks,
and logs are often burned, which kills much or all that is growing
above ground. In this way little maples, ashes, witch-hazels, willows,
huckleberries, blackberries, sweet ferns, service berries, aspens,
oaks, and others are often killed back, but afterward sprout up again
and again, and, after repeated burnings, form each a large rough mass
popularly known as a _grub_. The grubs of the oak are well known;
the large ones weighing from 75 to 100 pounds each. To plow land where
grubs abound requires a stout plow and several pairs of horses or
oxen.
A small white oak, after it has been many times killed to the ground,
dies in the middle and sprouts at the margins, and finally the main
root perishes, and two roots, with branches a little distance apart,
support each a cluster of stems above ground.
[Illustration: FIG. 2.--Small tree, "grub," of white oak many times
killed back; finally dead at the middle and sprouting on the margins.]
[Illustration: FIG. 3.--Grub, or remains of a white oak, doubtless
at one time much like Fig. 2, but now decayed in the middle, including
its main root; sprouting on the margins, farther and farther out after
the tops were killed, to the ground.]
[Illustration: FIG. 4.--Grub, or remains of a white oak, still older
than the one represented in Fig. 3. A hole appears where the tap root
has rotted away. The right-hand portion is already dividing, and in
time, if often killed back, we might find several distinct oaks as
descendants from one acorn.]
There can be no doubt that young oak trees slowly move in this manner
from one place to another. If in fifty years we have two distinct
grubs or branches, three or four feet apart, where the connecting
part has finally died out, I see no reason why in another fifty years
each one of the two may not again have spread and divided, giving
us at least four grubs, or clusters of sprouts, all originally coming
from one acorn; and so the matter might go on. This is slow traveling,
I admit, but there is nothing to hinder nature from taking all the
time she wants.
[Illustration: FIG. 5.--Part of a grub of white oak, still alive and
spreading over the ground, the central portions dying, the margins
alive and spreading.]