Notes of Lessons: Biology, Class III

[We have thought that it might be of use to our readers (in their own families) to publish from month to month during the current year, Notes of Lessons prepared by students of the House of Education for the pupils of the Practising School. We should like to say, however, that such a Lesson is never given as a tour de force, but is always an illustration or an expansion of some part of the children’s regular studies (in the Parents’ Review School), some passage in one or other of their school books.—Ed.]

Subject: Dispersion of Seeds • Group: Science • Class III • Time: 30 minutes

By E. Mary Pike
The Parents’ Review, 1903, pp. 306-307

Objects

I. To increase the children’s knowledge of plants.

II. To show how Nature adapts herself to her surroundings.

III. To give some account of the different ways by which the seeds of plants are distributed.

Lesson

Step I.—Ask why plants have various ways of distributing their seeds, and what would happen if they all fell close to the parent plant.

If all the seeds were to fall together they would not only be overshadowed by the parent plant, but would also be very much crowded, and so unable to obtain sufficient air and soil, which is necessary for their growth.

Step II.—Show specimens of seeds and fruits, and obtain from the children the different devices which plants make use of in providing for their seeds.

Some seeds are provided with wings—elm, sycamore, ash, pine, birch, etc. These are often blown to great distances by the wind, especially the birch, which is the lightest of all tree seeds. Others have plumes, such as the dandelion and most of the Compositæ, the willow-herb, etc. These act as parachutes to the seeds and enable them to be wafted on the slightest breeze. (Notice the spiny projection at the upper end of the dandelion seed, which prevents it from being blown out of the soil when it has once found a place.) Some plants, such as the cleavers, avens, burdock, etc., have hooks to their seeds, which enable them to cling to any animal or bird with which they may come in contact. Men, sheep, dogs, rabbits and birds often carry them to a distance in this way.

Some seeds are enclosed in succulent fruits, which, when ripe, are eaten by men or birds, thus liberating the seeds—cherry, blackberry, hip, haw, mistletoe, etc. Others are carried away in the mud which adheres to birds’ feet. (Mention Darwin’s observations on this point.) Some seeds are carried for long distances by water—plants on coral islands.

Seeds contained in pods are dispersed, when ripe, by the bursting of the pod—broom, bitter cress, etc.

Step III.—Point out how Nature adapts herself to her surroundings. Let the children notice that only the high plants have winged seeds and the lower ones hooks.

The dandelion when in flower remains in an upright position; having been fertilized, it lies on the ground until its seeds are mature, when it again raises itself so that the wind may be able the more easily to carry away its seeds.

Step IV.—Sum up the devices which are made use of in seed dispersion.