Ontario Teachers' Manuals: Nature Study

by Ontario. Department of Education

Study the flowers of the cucumber and compare them with those of the pumpkin.

CORN

This plant is native to America, was greatly prized by the aborigines, and even worshipped by some of them. Note the upright character of the plant and how the stalk is divided into sections by the joints, or nodes. Count these joints and also the leaves, and note the relationship of leaves and joints in the stalk, and how the leaves come off in different directions so as not to shade each other. Note the strong, stringy threads in the leaf, which give strength to the leaf as well as circulation of sap. They are strong and elastic, allowing of movement. The same strengthening fibres are seen in the stalk when it is broken across. In the stalk these fibres are arranged in a tubular form, as this gives greatest strength, the centre being soft and weak. The stalks are largest near the base, where the greatest stiffness is required. The nodes are also closer together here for strength. The stem is made much stronger by the bases of the leaves being wrapped so firmly around for a distance above the point of attachment at the node. Notice the close-fitting sheath or rain-guard, where the blade of the leaf leaves the stalk. This prevents rain soaking down inside the leaf sheath, but lets it run down the outside to the root where it is needed. As the plant gets older and taller, new roots come out from the node next above the root and sometimes from the second node above. These prop-roots are needed for support as the stalk lengthens, and they also reinforce the feeding capacity.

Note the appearance of little cobs in the axils of the leaves. As soon as the silk appears, take a cob off and open it carefully. The little cob, which corresponds to the pistil in other plants, is covered with small and undeveloped kernels, and to each kernel one of the strands of so-called silk is attached. Whilst this little cob is forming, a bunch, or tassel, of flowers is forming on the top of the corn plant. Open one of these flowers and find the stamens with pollen-grains inside. This pollen, when shed, falls upon the silk, and each grain sends a tiny tube down inside the silk to the delicate ovules on the cob, fertilizing them and starting them to develop. The silk then withers. The wind carries this pollen.

Find out how the silk is fitted for catching the pollen. What is the need for the great quantity of pollen that the plant produces?

Strip off the husks and compare the tough, hard husks that are found on the outside with the soft paper-like husks found close to the cob. Show how each kind is fitted for its particular work.

Pupils make experiments in the corn plot to find:

1. Whether the corn grows faster:

(1) When the soil is kept mellow or when the soil is hard;

(2) When the days are warm or when they are cool;