The wallflower family.—The plants of the family to which the wallflower belongs are of very great importance to mankind; for while not one of them is poisonous, many are extremely valuable as food-crops. They are all dicotyledons; that is, their seeds contain two cotyledons or “makeshift leaves,” as has already (Chapter I.) been seen in the case of the mustard. The net-like venation of the leaves of the full-grown plant also indicates this. There is a great family likeness between the flowers of this group, and they are easily recognised (Fig. 61 a, c) by the cross-shaped corolla and the six stamens (two short and four long). All the parts of the flower—sepals, [Pg 95] petals, stamens, and pistil—are fixed separately on the top of the flower stalk or receptacle. The cross-arrangement of the petals has led to these plants being called Crucifers (cross-bearers). The shepherd’s purse (Fig. 60)—so-called from the shape of its fruit—is a common weed with small, white flowers. All stages of the flower may generally be found on the same plant. While at the top the buds may still be unopened, the flowers below have been fertilised (in this case generally self-fertilised); the sepals, petals, and stamens—having fulfilled their duties—have fallen off; the ovules have become seeds, and the ovule-box or ovary has become a seed-box or fruit, consisting of two bags separated by a partition which bears two rows of seeds on each side (Fig. 62). Fig. 61.—Wild Radish. a, flower (nat. size); b, petal; c, stamens and pistil (× 2); d, pistil (× 2); e, fruit (× 1); f, cross section of fruit; g and h, embryo (mag.) Fig. 62.—A, Fruits of Shepherd’s Purse (× ½);Fig. 63.—Root of Fig. 64.—Root B, a single open fruit (mag.); C, cross section of B. Turnip. (× ⅓.)of Radish. (× ½.) Useful crucifers.—The turnip and the radish are largely cultivated for their roots (Figs. 63 and 64), and are then taken out of [Pg 96] the ground at the end of their first season. As these plants naturally flower in their second year of growth and then die, they are called biennials. The production of flowers and fruit is a great strain on a plant, and it is to prepare for the effort that the turnip and radish store so much food in their roots during the first year as to give them a globular and spindle shape respectively. A carrot is not a crucifer, but it also adopts this device. The cabbage is grown for its leaves. Varieties of the cabbage are Brussels sprouts, broccoli, and cauliflower; it is the very small flower-buds of the last two which are eaten. Cress and white mustard are eaten in the seedling stage. The seeds of the black mustard are ground and eaten as a condiment. 17. THE BUTTERCUP FAMILY. 1. The buttercup.—Notice the habit of growth, characters of the leaves, etc. Is the buttercup a dicotyledon? Make this observation with all flowering plants. (See, however, Chap. VIII., p. 163.)