The larvæ of the cabbage-butterfly sometimes do a great deal of harm by eating the cabbage leaves. It will not do to use paris-green on cabbage, as the leaves are for eating. Instead, use pyrethrum or insect powder, which may be diluted by mixing with cheap flour—one ounce of insect powder to five of flour. Mix thoroughly and leave in a closed tin over night. Dust the mixture on the leaves from a cheese-cloth bag by tapping with a small stick or from a dusting-pan. If used while the dew is on the leaves, it sticks better. Insect powder is not poisonous to man as is paris-green, and so may be used freely on cabbage or other similar plants.
PLANTS
ANNUALS, BIENNIALS, AND PERENNIALS
CLASS-ROOM LESSON
By means of questions based upon the pupils' knowledge of a few common annuals, such as the oat, sweet-pea, and garden aster, develop the following points:
1. These plants are always grown from seeds.
2. These plants produce flowers and ripe seeds during one season's growth.
3. These plants wither and die in the autumn.
Plants having these characteristics are called annuals. The teacher explains the meaning of the word and requires the pupils to name a few other annuals.
In a similar way, discuss a few common types of biennials, such as turnip, cabbage, hollyhock, and develop the following points: