Notes of Lessons: Biology, Class II

[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: The Dispersion of Seeds • Group: Nature Lore • Class II • Time: 30 minutes

By M. Mart
The Parents’ Review, 1904, pp. 714-716

Objects

I. To stimulate the children’s love and admiration for nature, by bringing before their notice some of her ingenious methods for propagating plants.

II. To draw from the children all that they have observed for themselves about the manner in which the seeds get carried about, and the different coverings they have. Also to distinguish between fruit and seed.

Lesson

Step I.—Ask the children where the plants get most of their food from. The soil. But different kinds of plants need different foods, the peas and beans take lime, turnips and potatoes take potash from the soil. Ask the children what would happen if the same kind of plant lived in the same place year after year, and multiplied accordingly. The food which those plants need would soon become exhausted, or they would choke one another. To prevent this the parent plant has a system of her own. Draw from the children that she sends away her little seeds, and some of her methods. By wings, by hairs, by hooks which fasten on to animals, etc.

Step II.—But the hooks and wings are no use without something else to help them on their way. The living creatures to carry away the hooked seeds and the wind for the winged ones. Ask what kind of seeds are carried away by the wind, and on what kind of plant do we have winged seeds? On high ones, generally trees. Why is this? Because having plenty of surface the plumed seeds fall slowly, and as they are descending from a considerable height, the wind has opportunity to catch the seed and blow it to a distance. Let one of the children hold up two sycamore seeds, the one with its plumes and the other without, drop them and see how much more slowly the plumed seed falls to the ground. Show the children the seeds of the ash, willow, etc. Show seeds of the firs, larches, etc., give these as examples of seeds which are naked. Seeds upon low, plants having only a little way to fall, need something to take them upward which shall be lighter than wings, so they are provided with the lightest of light hairs. Ask the children to name some plants having seeds with hairs. Show them the dandelion, willow herb, thistle, etc. Show the seed in the open pod in the willow herb, take one out, see how the hairs orcilia at once spread out. Let it float away from the fingers without being blown, and it will be lost to sight against the ceiling very soon.

Step III.—Show the children seeds which have hooks. Burdock, and teasel, and the stickyballs of goose-grass, and the seed of the forget-me-not. The children will say that they are carried about by animals, they stick into the fur or wool, and at some time before long get rubbed off. Tell them that the teasel is used by cloth manufacturers to “tease” the surface of the woven cloth, that is, to scratch it and raise the pile or hairs.

Step IV.—Draw from the children other kinds of seed and how they are dispersed, those which explode and those which are carried about by birds, or eaten by them. Ask if they know the balsam, or touch-me-not. Have some pods of ripe balsam, which the children can touch themselves and see the explosion of the seeds. Show the broom pod shut and one which has discharged, the sides open and twisted.

Step V.—Ask the children to think of the rose hip, and to say where the seeds are, how they are scattered. If they think they do not know how they are scattered, ask them if they have not seen many hips half eaten still on the stem. Show one eaten by a bird with the seeds inside. Do the birds eat the seeds? No. They like the bright outer covering, but the little seeds inside are poisonous to them. So the seeds have a rough and sticky outer covering. If the bird tries to swallow one, it sticks in his throat and would choke him, so he has to put it out again. Draw from the children that many seeds have soft juicy coverings, namely, berries; get them to mention some—elder, mountain ash, guelder rose, black bryony, bitter sweet, honeysuckle and haws.

Step VI.—Mention briefly that seeds can float on the water for some time; these have cilae, by which means they can propel themselves. Darwin has calculated that a seed may remain for twenty-eight days in the water without being damaged. The spores of mosses and ferns are often carried to a great distance in this way. In the mud clinging to the feet of birds, many seeds are carried; aquatic birds also carry them on their wings and sticking to their beaks, from one river or lake to another. Darwin made a careful experiment; a wounded partridge had a ball of earth weighing 6 1/2 ozs. adhering to its legs, and from this earth he reared no less than eighty-two separate plants.