Wind Dispersal of Seeds

 

 

One thing the foresters had to learn by experience in selecting the groups to be left for “mother –trees” was that they should be on the ridges and higher points of land where they are most exposed to the winds, so that the seeds will be carried as far as possible. And yet I suppose practically all of us know perfectly well that seeds fly “ on the wings of the wind”, to us the grand, poetic phrase of the Bible; which only goes to show again that we may have valuable information in our heads and yet fail to put it to use at first, when some occasion requires it.

The Linden has a regular flying-machine, a monoplane, and one that carries several passengers at a time. In ordinary winds the wing of seeds do not keep them long afloat; and even in a fairly strong breeze, they seldom travel more than two or three times the height of the tree. I am speaking of such seeds as those of the Maple and the Linden. The little Pine-seeds are carried much farther. And the tufts on the seeds of the Pussy-Willows and their kin, While they are not what a bird would call wings at all, I suppose, keep them afloat in a wind of only two miles an hour.

And some of these winged seeds have flying tricks that help. A Pine-seed, for example, carries its little wing in such a position that the seed whirls as it falls, and so it descends very slowly. See the advantage of that? This increases its chances of catching any outbound trains among passing wind currents. It may thus be able to take long journeys simply by “changing cars” from time to time. A horizontal puff may carry it out and away from the parent tree; then another, an upbound current, may carry it to where there are stronger breezes and where its movements are less likely to be interfered with by other trees. In very strong winds not only Pines but other winged seeds may be carried several miles. This explains why you find trees like Gray Birch and the White Pine growing in the middle of pastures, far away from the woods.

 

How the Pine-seeds put on their wings

Because the Pine –seeds are such clever travelers and can, in their different species, accommodate themselves to so many varieties of soil and climate, you find them everywhere- on barren wastes, on the edges of rivers and lakes, or climbing the mountains to the timber-line, or clear on the borders of salt water, where no other tree dare go, bravely facing the fierce winds from the sea.

The cones mature the second or third year after flowering. The seeds are in pairs, attached at the base, in shallow depressions, to the inner surface of the scales. As they fall from the cone they take with them the thin lining of the cone scales, and these are their wings.

Yet they are delicate little bodies, these seeds, and must not be allowed to become too dry or they will not grow.

 

Queer hoop-chasing by the wind sprite

 

But the seeds of a tree do not necessarily have to have wings in order to be helped along by the wind. Even the Oaks, and nut-bearing trees like the Hickory, get a lift now and then in a threshing gale, but the Locust has a special device. Have not you noticed how its big “pea-pods”- it belongs to the pea family, by the way-in drying, contract and so become twisted and curled? And then did you ever see them go rolling before a stiff breeze? It is a queer sort of hoop-chasing on the part of the wind sprites; but what these wind sprites are really doing, from a practical standpoint, is distributing the seeds of the Locust.

 

Exercises:

 

1Name the species you found in the text.

 

2Find the Russian/English equivalents:

-to keep afloat

-tufts on the seeds

-to have flying tricks

-to travel 2 times the height of the tree

-to mature

-крылатое семечко

-легкий ветер

-материнское дерево

-поток ветра

-шишка

 

3 Translate the verbs and find them in the text:

 

to whirl-to fall-to descend –to carry -to fly

 

 

4While reading the text you met “wind” and “breeze”

a) What is the difference between them?

b) Find all the word combinations with these words.

5 Answer the questions:

a) What is the advantage of the Linden regular flying machine?

b) What helps a Pine seed to descend slowly?

c) What seeds travel farther?

d) Where can you find pines?

e) What are (is) the advantage(s) of doubled pine seeds attached at the base?

f) What species have heavy seeds?

g) How do the seeds of these trees travel?

 

Text 5